diff --git a/src/init.cpp b/src/init.cpp
index e75e981a5..dcd65198c 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -116,7 +116,7 @@ void Shutdown()
     {
         LOCK(cs_main);
         if (pwalletMain)
-            pwalletMain->SetBestChain(CBlockLocator(pindexBest));
+            pwalletMain->SetBestChain(CBlockLocator(chainActive.Tip()));
         if (pblocktree)
             pblocktree->Flush();
         if (pcoinsTip)
@@ -766,7 +766,7 @@ bool AppInit2(boost::thread_group& threadGroup)
 
                 // If the loaded chain has a wrong genesis, bail out immediately
                 // (we're likely using a testnet datadir, or the other way around).
-                if (!mapBlockIndex.empty() && pindexGenesisBlock == NULL)
+                if (!mapBlockIndex.empty() && chainActive.Genesis() == NULL)
                     return InitError(_("Incorrect or no genesis block found. Wrong datadir for network?"));
 
                 // Initialize the block index (no-op if non-empty database was already loaded)
@@ -912,7 +912,7 @@ bool AppInit2(boost::thread_group& threadGroup)
                 strErrors << _("Cannot write default address") << "\n";
         }
 
-        pwalletMain->SetBestChain(CBlockLocator(pindexBest));
+        pwalletMain->SetBestChain(CBlockLocator(chainActive.Tip()));
     }
 
     LogPrintf("%s", strErrors.str().c_str());
@@ -920,9 +920,9 @@ bool AppInit2(boost::thread_group& threadGroup)
 
     RegisterWallet(pwalletMain);
 
-    CBlockIndex *pindexRescan = pindexBest;
+    CBlockIndex *pindexRescan = chainActive.Tip();
     if (GetBoolArg("-rescan", false))
-        pindexRescan = pindexGenesisBlock;
+        pindexRescan = chainActive.Genesis();
     else
     {
         CWalletDB walletdb(strWalletFile);
@@ -930,16 +930,16 @@ bool AppInit2(boost::thread_group& threadGroup)
         if (walletdb.ReadBestBlock(locator))
             pindexRescan = locator.GetBlockIndex();
         else
-            pindexRescan = pindexGenesisBlock;
+            pindexRescan = chainActive.Genesis();
     }
-    if (pindexBest && pindexBest != pindexRescan)
+    if (chainActive.Tip() && chainActive.Tip() != pindexRescan)
     {
         uiInterface.InitMessage(_("Rescanning..."));
-        LogPrintf("Rescanning last %i blocks (from block %i)...\n", pindexBest->nHeight - pindexRescan->nHeight, pindexRescan->nHeight);
+        LogPrintf("Rescanning last %i blocks (from block %i)...\n", chainActive.Height() - pindexRescan->nHeight, pindexRescan->nHeight);
         nStart = GetTimeMillis();
         pwalletMain->ScanForWalletTransactions(pindexRescan, true);
         LogPrintf(" rescan      %15"PRI64d"ms\n", GetTimeMillis() - nStart);
-        pwalletMain->SetBestChain(CBlockLocator(pindexBest));
+        pwalletMain->SetBestChain(CBlockLocator(chainActive.Tip()));
         nWalletDBUpdated++;
     }
 
@@ -985,7 +985,7 @@ bool AppInit2(boost::thread_group& threadGroup)
 
     //// debug print
     LogPrintf("mapBlockIndex.size() = %"PRIszu"\n",   mapBlockIndex.size());
-    LogPrintf("nBestHeight = %d\n",                   nBestHeight);
+    LogPrintf("nBestHeight = %d\n",                   chainActive.Height());
     LogPrintf("setKeyPool.size() = %"PRIszu"\n",      pwalletMain ? pwalletMain->setKeyPool.size() : 0);
     LogPrintf("mapWallet.size() = %"PRIszu"\n",       pwalletMain ? pwalletMain->mapWallet.size() : 0);
     LogPrintf("mapAddressBook.size() = %"PRIszu"\n",  pwalletMain ? pwalletMain->mapAddressBook.size() : 0);
diff --git a/src/main.cpp b/src/main.cpp
index 5ce330a9d..732a82852 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -32,13 +32,8 @@ CTxMemPool mempool;
 unsigned int nTransactionsUpdated = 0;
 
 map<uint256, CBlockIndex*> mapBlockIndex;
-std::vector<CBlockIndex*> vBlockIndexByHeight;
-CBlockIndex* pindexGenesisBlock = NULL;
-int nBestHeight = -1;
-uint256 nBestChainWork = 0;
+CChain chainActive;
 uint256 nBestInvalidWork = 0;
-uint256 hashBestChain = 0;
-CBlockIndex* pindexBest = NULL;
 set<CBlockIndex*, CBlockIndexWorkComparator> setBlockIndexValid; // may contain all CBlockIndex*'s that have validness >=BLOCK_VALID_TRANSACTIONS, and must contain those who aren't failed
 int64 nTimeBestReceived = 0;
 int nScriptCheckThreads = 0;
@@ -173,14 +168,22 @@ void static ResendWalletTransactions()
 // Registration of network node signals.
 //
 
+int static GetHeight()
+{
+    LOCK(cs_main);
+    return chainActive.Height();
+}
+
 void RegisterNodeSignals(CNodeSignals& nodeSignals)
 {
+    nodeSignals.GetHeight.connect(&GetHeight);
     nodeSignals.ProcessMessages.connect(&ProcessMessages);
     nodeSignals.SendMessages.connect(&SendMessages);
 }
 
 void UnregisterNodeSignals(CNodeSignals& nodeSignals)
 {
+    nodeSignals.GetHeight.disconnect(&GetHeight);
     nodeSignals.ProcessMessages.disconnect(&ProcessMessages);
     nodeSignals.SendMessages.disconnect(&SendMessages);
 }
@@ -225,7 +228,7 @@ int CBlockLocator::GetDistanceBack()
         if (mi != mapBlockIndex.end())
         {
             CBlockIndex* pindex = (*mi).second;
-            if (pindex->IsInMainChain())
+            if (chainActive.Contains(pindex))
                 return nDistance;
         }
         nDistance += nStep;
@@ -244,11 +247,11 @@ CBlockIndex *CBlockLocator::GetBlockIndex()
         if (mi != mapBlockIndex.end())
         {
             CBlockIndex* pindex = (*mi).second;
-            if (pindex->IsInMainChain())
+            if (chainActive.Contains(pindex))
                 return pindex;
         }
     }
-    return pindexGenesisBlock;
+    return chainActive.Genesis();
 }
 
 uint256 CBlockLocator::GetBlockHash()
@@ -260,7 +263,7 @@ uint256 CBlockLocator::GetBlockHash()
         if (mi != mapBlockIndex.end())
         {
             CBlockIndex* pindex = (*mi).second;
-            if (pindex->IsInMainChain())
+            if (chainActive.Contains(pindex))
                 return hash;
         }
     }
@@ -275,6 +278,19 @@ int CBlockLocator::GetHeight()
     return pindex->nHeight;
 }
 
+CBlockIndex *CChain::SetTip(CBlockIndex *pindex) {
+    if (pindex == NULL) {
+        std::vector<CBlockIndex*>().swap(vChain);
+        return NULL;
+    }
+    vChain.resize(pindex->nHeight + 1);
+    while (pindex && vChain[pindex->nHeight] != pindex) {
+        vChain[pindex->nHeight] = pindex;
+        pindex = pindex->pprev;
+    }
+    return pindex;
+}
+
 //////////////////////////////////////////////////////////////////////////////
 //
 // CCoinsView implementations
@@ -517,7 +533,7 @@ bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64 nBlockTime)
     if (tx.nLockTime == 0)
         return true;
     if (nBlockHeight == 0)
-        nBlockHeight = nBestHeight;
+        nBlockHeight = chainActive.Height();
     if (nBlockTime == 0)
         nBlockTime = GetAdjustedTime();
     if ((int64)tx.nLockTime < ((int64)tx.nLockTime < LOCKTIME_THRESHOLD ? (int64)nBlockHeight : nBlockTime))
@@ -644,7 +660,7 @@ int CMerkleTx::SetMerkleBranch(const CBlock* pblock)
     if (pblock == NULL) {
         CCoins coins;
         if (pcoinsTip->GetCoins(GetHash(), coins)) {
-            CBlockIndex *pindex = FindBlockByHeight(coins.nHeight);
+            CBlockIndex *pindex = chainActive[coins.nHeight];
             if (pindex) {
                 if (!ReadBlockFromDisk(blockTmp, pindex))
                     return 0;
@@ -678,10 +694,10 @@ int CMerkleTx::SetMerkleBranch(const CBlock* pblock)
     if (mi == mapBlockIndex.end())
         return 0;
     CBlockIndex* pindex = (*mi).second;
-    if (!pindex || !pindex->IsInMainChain())
+    if (!pindex || !chainActive.Contains(pindex))
         return 0;
 
-    return pindexBest->nHeight - pindex->nHeight + 1;
+    return chainActive.Height() - pindex->nHeight + 1;
 }
 
 
@@ -1078,7 +1094,7 @@ int CMerkleTx::GetDepthInMainChain(CBlockIndex* &pindexRet) const
     if (mi == mapBlockIndex.end())
         return 0;
     CBlockIndex* pindex = (*mi).second;
-    if (!pindex || !pindex->IsInMainChain())
+    if (!pindex || !chainActive.Contains(pindex))
         return 0;
 
     // Make sure the merkle branch connects to this block
@@ -1090,7 +1106,7 @@ int CMerkleTx::GetDepthInMainChain(CBlockIndex* &pindexRet) const
     }
 
     pindexRet = pindex;
-    return pindexBest->nHeight - pindex->nHeight + 1;
+    return chainActive.Height() - pindex->nHeight + 1;
 }
 
 
@@ -1173,7 +1189,7 @@ bool GetTransaction(const uint256 &hash, CTransaction &txOut, uint256 &hashBlock
                     nHeight = coins.nHeight;
             }
             if (nHeight > 0)
-                pindexSlow = FindBlockByHeight(nHeight);
+                pindexSlow = chainActive[nHeight];
         }
     }
 
@@ -1203,14 +1219,6 @@ bool GetTransaction(const uint256 &hash, CTransaction &txOut, uint256 &hashBlock
 // CBlock and CBlockIndex
 //
 
-static CBlockIndex* pblockindexFBBHLast;
-CBlockIndex* FindBlockByHeight(int nHeight)
-{
-    if (nHeight >= (int)vBlockIndexByHeight.size())
-        return NULL;
-    return vBlockIndexByHeight[nHeight];
-}
-
 bool WriteBlockToDisk(CBlock& block, CDiskBlockPos& pos)
 {
     // Open history file to append
@@ -1404,17 +1412,17 @@ int GetNumBlocksOfPeers()
 
 bool IsInitialBlockDownload()
 {
-    if (pindexBest == NULL || fImporting || fReindex || nBestHeight < Checkpoints::GetTotalBlocksEstimate())
+    if (fImporting || fReindex || chainActive.Height() < Checkpoints::GetTotalBlocksEstimate())
         return true;
     static int64 nLastUpdate;
     static CBlockIndex* pindexLastBest;
-    if (pindexBest != pindexLastBest)
+    if (chainActive.Tip() != pindexLastBest)
     {
-        pindexLastBest = pindexBest;
+        pindexLastBest = chainActive.Tip();
         nLastUpdate = GetTime();
     }
     return (GetTime() - nLastUpdate < 10 &&
-            pindexBest->GetBlockTime() < GetTime() - 24 * 60 * 60);
+            chainActive.Tip()->GetBlockTime() < GetTime() - 24 * 60 * 60);
 }
 
 bool fLargeWorkForkFound = false;
@@ -1430,10 +1438,10 @@ void CheckForkWarningConditions()
 
     // If our best fork is no longer within 72 blocks (+/- 12 hours if no one mines it)
     // of our head, drop it
-    if (pindexBestForkTip && nBestHeight - pindexBestForkTip->nHeight >= 72)
+    if (pindexBestForkTip && chainActive.Height() - pindexBestForkTip->nHeight >= 72)
         pindexBestForkTip = NULL;
 
-    if (pindexBestForkTip || nBestInvalidWork > nBestChainWork + (pindexBest->GetBlockWork() * 6).getuint256())
+    if (pindexBestForkTip || nBestInvalidWork > chainActive.Tip()->nChainWork + (chainActive.Tip()->GetBlockWork() * 6).getuint256())
     {
         if (!fLargeWorkForkFound)
         {
@@ -1470,7 +1478,7 @@ void CheckForkWarningConditionsOnNewFork(CBlockIndex* pindexNewForkTip)
 {
     // If we are on a fork that is sufficiently large, set a warning flag
     CBlockIndex* pfork = pindexNewForkTip;
-    CBlockIndex* plonger = pindexBest;
+    CBlockIndex* plonger = chainActive.Tip();
     while (pfork && pfork != plonger)
     {
         while (plonger && plonger->nHeight > pfork->nHeight)
@@ -1489,7 +1497,7 @@ void CheckForkWarningConditionsOnNewFork(CBlockIndex* pindexNewForkTip)
     // the 7-block condition and from this always have the most-likely-to-cause-warning fork
     if (pfork && (!pindexBestForkTip || (pindexBestForkTip && pindexNewForkTip->nHeight > pindexBestForkTip->nHeight)) &&
             pindexNewForkTip->nChainWork - pfork->nChainWork > (pfork->GetBlockWork() * 7).getuint256() &&
-            nBestHeight - pindexNewForkTip->nHeight < 72)
+            chainActive.Height() - pindexNewForkTip->nHeight < 72)
     {
         pindexBestForkTip = pindexNewForkTip;
         pindexBestForkBase = pfork;
@@ -1511,8 +1519,8 @@ void static InvalidChainFound(CBlockIndex* pindexNew)
       log(pindexNew->nChainWork.getdouble())/log(2.0), DateTimeStrFormat("%Y-%m-%d %H:%M:%S",
       pindexNew->GetBlockTime()).c_str());
     LogPrintf("InvalidChainFound:  current best=%s  height=%d  log2_work=%.8g  date=%s\n",
-      hashBestChain.ToString().c_str(), nBestHeight, log(nBestChainWork.getdouble())/log(2.0),
-      DateTimeStrFormat("%Y-%m-%d %H:%M:%S", pindexBest->GetBlockTime()).c_str());
+      chainActive.Tip()->GetBlockHash().ToString().c_str(), chainActive.Height(), log(chainActive.Tip()->nChainWork.getdouble())/log(2.0),
+      DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()).c_str());
     CheckForkWarningConditions();
 }
 
@@ -1521,7 +1529,7 @@ void static InvalidBlockFound(CBlockIndex *pindex) {
     pblocktree->WriteBlockIndex(CDiskBlockIndex(pindex));
     setBlockIndexValid.erase(pindex);
     InvalidChainFound(pindex);
-    if (pindex->GetNextInMainChain()) {
+    if (chainActive.Next(pindex)) {
         CValidationState stateDummy;
         ConnectBestBlock(stateDummy); // reorganise away from the failed block
     }
@@ -1538,7 +1546,7 @@ bool ConnectBestBlock(CValidationState &state) {
             pindexNewBest = *it;
         }
 
-        if (pindexNewBest == pindexBest || (pindexBest && pindexNewBest->nChainWork == pindexBest->nChainWork))
+        if (pindexNewBest == chainActive.Tip() || (chainActive.Tip() && pindexNewBest->nChainWork == chainActive.Tip()->nChainWork))
             return true; // nothing to do
 
         // check ancestry
@@ -1558,10 +1566,10 @@ bool ConnectBestBlock(CValidationState &state) {
                 break;
             }
 
-            if (pindexBest == NULL || pindexTest->nChainWork > pindexBest->nChainWork)
+            if (chainActive.Tip() == NULL || pindexTest->nChainWork > chainActive.Tip()->nChainWork)
                 vAttach.push_back(pindexTest);
 
-            if (pindexTest->pprev == NULL || pindexTest->GetNextInMainChain()) {
+            if (pindexTest->pprev == NULL || chainActive.Next(pindexTest)) {
                 reverse(vAttach.begin(), vAttach.end());
                 BOOST_FOREACH(CBlockIndex *pindexSwitch, vAttach) {
                     boost::this_thread::interruption_point();
@@ -1881,7 +1889,6 @@ bool ConnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex, C
     // (its coinbase is unspendable)
     if (block.GetHash() == Params().HashGenesisBlock()) {
         view.SetBestBlock(pindex);
-        pindexGenesisBlock = pindex;
         return true;
     }
 
@@ -2129,9 +2136,7 @@ bool SetBestChain(CValidationState &state, CBlockIndex* pindexNew)
     // Proceed by updating the memory structures.
 
     // Register new best chain
-    vBlockIndexByHeight.resize(pindexNew->nHeight + 1);
-    BOOST_FOREACH(CBlockIndex* pindex, vConnect)
-        vBlockIndexByHeight[pindex->nHeight] = pindex;
+    chainActive.SetTip(pindexNew);
 
     // Resurrect memory transactions that were in the disconnected branch
     BOOST_FOREACH(CTransaction& tx, vResurrect) {
@@ -2157,23 +2162,18 @@ bool SetBestChain(CValidationState &state, CBlockIndex* pindexNew)
     }
 
     // New best block
-    hashBestChain = pindexNew->GetBlockHash();
-    pindexBest = pindexNew;
-    pblockindexFBBHLast = NULL;
-    nBestHeight = pindexBest->nHeight;
-    nBestChainWork = pindexNew->nChainWork;
     nTimeBestReceived = GetTime();
     nTransactionsUpdated++;
     LogPrintf("SetBestChain: new best=%s  height=%d  log2_work=%.8g  tx=%lu  date=%s progress=%f\n",
-      hashBestChain.ToString().c_str(), nBestHeight, log(nBestChainWork.getdouble())/log(2.0), (unsigned long)pindexNew->nChainTx,
-      DateTimeStrFormat("%Y-%m-%d %H:%M:%S", pindexBest->GetBlockTime()).c_str(),
-      Checkpoints::GuessVerificationProgress(pindexBest));
+      chainActive.Tip()->GetBlockHash().ToString().c_str(), chainActive.Height(), log(chainActive.Tip()->nChainWork.getdouble())/log(2.0), (unsigned long)pindexNew->nChainTx,
+      DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()).c_str(),
+      Checkpoints::GuessVerificationProgress(chainActive.Tip()));
 
     // Check the version of the last 100 blocks to see if we need to upgrade:
     if (!fIsInitialDownload)
     {
         int nUpgraded = 0;
-        const CBlockIndex* pindex = pindexBest;
+        const CBlockIndex* pindex = chainActive.Tip();
         for (int i = 0; i < 100 && pindex != NULL; i++)
         {
             if (pindex->nVersion > CBlock::CURRENT_VERSION)
@@ -2191,7 +2191,7 @@ bool SetBestChain(CValidationState &state, CBlockIndex* pindexNew)
 
     if (!fIsInitialDownload && !strCmd.empty())
     {
-        boost::replace_all(strCmd, "%s", hashBestChain.GetHex());
+        boost::replace_all(strCmd, "%s", chainActive.Tip()->GetBlockHash().GetHex());
         boost::thread t(runCommand, strCmd); // thread runs free
     }
 
@@ -2233,7 +2233,7 @@ bool AddToBlockIndex(CBlock& block, CValidationState& state, const CDiskBlockPos
     if (!ConnectBestBlock(state))
         return false;
 
-    if (pindexNew == pindexBest)
+    if (pindexNew == chainActive.Tip())
     {
         // Clear fork warning if its no longer applicable
         CheckForkWarningConditions();
@@ -2482,11 +2482,11 @@ bool AcceptBlock(CBlock& block, CValidationState& state, CDiskBlockPos* dbp)
 
     // Relay inventory, but don't relay old inventory during initial block download
     int nBlockEstimate = Checkpoints::GetTotalBlocksEstimate();
-    if (hashBestChain == hash)
+    if (chainActive.Tip()->GetBlockHash() == hash)
     {
         LOCK(cs_vNodes);
         BOOST_FOREACH(CNode* pnode, vNodes)
-            if (nBestHeight > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : nBlockEstimate))
+            if (chainActive.Height() > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : nBlockEstimate))
                 pnode->PushInventory(CInv(MSG_BLOCK, hash));
     }
 
@@ -2505,6 +2505,18 @@ bool CBlockIndex::IsSuperMajority(int minVersion, const CBlockIndex* pstart, uns
     return (nFound >= nRequired);
 }
 
+int64 CBlockIndex::GetMedianTime() const
+{
+    const CBlockIndex* pindex = this;
+    for (int i = 0; i < nMedianTimeSpan/2; i++)
+    {
+        if (!chainActive.Next(pindex))
+            return GetBlockTime();
+        pindex = chainActive.Next(pindex);
+    }
+    return pindex->GetMedianTimePast();
+}
+
 void PushGetBlocks(CNode* pnode, CBlockIndex* pindexBegin, uint256 hashEnd)
 {
     // Filter out duplicate requests
@@ -2530,7 +2542,7 @@ bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBl
         return error("ProcessBlock() : CheckBlock FAILED");
 
     CBlockIndex* pcheckpoint = Checkpoints::GetLastCheckpoint(mapBlockIndex);
-    if (pcheckpoint && pblock->hashPrevBlock != hashBestChain)
+    if (pcheckpoint && pblock->hashPrevBlock != (chainActive.Tip() ? chainActive.Tip()->GetBlockHash() : uint256(0)))
     {
         // Extra checks to prevent "fill up memory by spamming with bogus blocks"
         int64 deltaTime = pblock->GetBlockTime() - pcheckpoint->nTime;
@@ -2561,7 +2573,7 @@ bool ProcessBlock(CValidationState &state, CNode* pfrom, CBlock* pblock, CDiskBl
             mapOrphanBlocksByPrev.insert(make_pair(pblock2->hashPrevBlock, pblock2));
 
             // Ask this guy to fill in what we're missing
-            PushGetBlocks(pfrom, pindexBest, GetOrphanRoot(pblock2));
+            PushGetBlocks(pfrom, chainActive.Tip(), GetOrphanRoot(pblock2));
         }
         return true;
     }
@@ -2875,48 +2887,39 @@ bool static LoadBlockIndexDB()
     LogPrintf("LoadBlockIndexDB(): transaction index %s\n", fTxIndex ? "enabled" : "disabled");
 
     // Load hashBestChain pointer to end of best chain
-    pindexBest = pcoinsTip->GetBestBlock();
-    if (pindexBest == NULL)
+    chainActive.SetTip(pcoinsTip->GetBestBlock());
+    if (chainActive.Tip() == NULL)
         return true;
-    hashBestChain = pindexBest->GetBlockHash();
-    nBestHeight = pindexBest->nHeight;
-    nBestChainWork = pindexBest->nChainWork;
 
     // register best chain
-    CBlockIndex *pindex = pindexBest;
-    vBlockIndexByHeight.resize(pindexBest->nHeight + 1);
-    while(pindex != NULL) {
-         vBlockIndexByHeight[pindex->nHeight] = pindex;
-         pindex = pindex->pprev;
-    }
     LogPrintf("LoadBlockIndexDB(): hashBestChain=%s  height=%d date=%s\n",
-        hashBestChain.ToString().c_str(), nBestHeight,
-        DateTimeStrFormat("%Y-%m-%d %H:%M:%S", pindexBest->GetBlockTime()).c_str());
+        chainActive.Tip()->GetBlockHash().ToString().c_str(), chainActive.Height(),
+        DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()).c_str());
 
     return true;
 }
 
 bool VerifyDB(int nCheckLevel, int nCheckDepth)
 {
-    if (pindexBest == NULL || pindexBest->pprev == NULL)
+    if (chainActive.Tip() == NULL || chainActive.Tip()->pprev == NULL)
         return true;
 
     // Verify blocks in the best chain
     if (nCheckDepth <= 0)
         nCheckDepth = 1000000000; // suffices until the year 19000
-    if (nCheckDepth > nBestHeight)
-        nCheckDepth = nBestHeight;
+    if (nCheckDepth > chainActive.Height())
+        nCheckDepth = chainActive.Height();
     nCheckLevel = std::max(0, std::min(4, nCheckLevel));
     LogPrintf("Verifying last %i blocks at level %i\n", nCheckDepth, nCheckLevel);
     CCoinsViewCache coins(*pcoinsTip, true);
-    CBlockIndex* pindexState = pindexBest;
+    CBlockIndex* pindexState = chainActive.Tip();
     CBlockIndex* pindexFailure = NULL;
     int nGoodTransactions = 0;
     CValidationState state;
-    for (CBlockIndex* pindex = pindexBest; pindex && pindex->pprev; pindex = pindex->pprev)
+    for (CBlockIndex* pindex = chainActive.Tip(); pindex && pindex->pprev; pindex = pindex->pprev)
     {
         boost::this_thread::interruption_point();
-        if (pindex->nHeight < nBestHeight-nCheckDepth)
+        if (pindex->nHeight < chainActive.Height()-nCheckDepth)
             break;
         CBlock block;
         // check level 0: read from disk
@@ -2948,14 +2951,14 @@ bool VerifyDB(int nCheckLevel, int nCheckDepth)
         }
     }
     if (pindexFailure)
-        return error("VerifyDB() : *** coin database inconsistencies found (last %i blocks, %i good transactions before that)\n", pindexBest->nHeight - pindexFailure->nHeight + 1, nGoodTransactions);
+        return error("VerifyDB() : *** coin database inconsistencies found (last %i blocks, %i good transactions before that)\n", chainActive.Height() - pindexFailure->nHeight + 1, nGoodTransactions);
 
     // check level 4: try reconnecting blocks
     if (nCheckLevel >= 4) {
         CBlockIndex *pindex = pindexState;
-        while (pindex != pindexBest) {
+        while (pindex != chainActive.Tip()) {
             boost::this_thread::interruption_point();
-            pindex = pindex->GetNextInMainChain();
+            pindex = chainActive.Next(pindex);
             CBlock block;
             if (!ReadBlockFromDisk(block, pindex))
                 return error("VerifyDB() : *** ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString().c_str());
@@ -2964,7 +2967,7 @@ bool VerifyDB(int nCheckLevel, int nCheckDepth)
         }
     }
 
-    LogPrintf("No coin database inconsistencies in last %i blocks (%i transactions)\n", pindexBest->nHeight - pindexState->nHeight, nGoodTransactions);
+    LogPrintf("No coin database inconsistencies in last %i blocks (%i transactions)\n", chainActive.Height() - pindexState->nHeight, nGoodTransactions);
 
     return true;
 }
@@ -2973,12 +2976,8 @@ void UnloadBlockIndex()
 {
     mapBlockIndex.clear();
     setBlockIndexValid.clear();
-    pindexGenesisBlock = NULL;
-    nBestHeight = 0;
-    nBestChainWork = 0;
+    chainActive.SetTip(NULL);
     nBestInvalidWork = 0;
-    hashBestChain = 0;
-    pindexBest = NULL;
 }
 
 bool LoadBlockIndex()
@@ -2992,7 +2991,7 @@ bool LoadBlockIndex()
 
 bool InitBlockIndex() {
     // Check whether we're already initialized
-    if (pindexGenesisBlock != NULL)
+    if (chainActive.Genesis() != NULL)
         return true;
 
     // Use the provided setting for -txindex in the new database
@@ -3038,7 +3037,7 @@ void PrintBlockTree()
     }
 
     vector<pair<int, CBlockIndex*> > vStack;
-    vStack.push_back(make_pair(0, pindexGenesisBlock));
+    vStack.push_back(make_pair(0, chainActive.Genesis()));
 
     int nPrevCol = 0;
     while (!vStack.empty())
@@ -3081,7 +3080,7 @@ void PrintBlockTree()
         vector<CBlockIndex*>& vNext = mapNext[pindex];
         for (unsigned int i = 0; i < vNext.size(); i++)
         {
-            if (vNext[i]->GetNextInMainChain())
+            if (chainActive.Next(vNext[i]))
             {
                 swap(vNext[0], vNext[i]);
                 break;
@@ -3328,7 +3327,7 @@ void static ProcessGetData(CNode* pfrom)
                         // and we want it right after the last block so they don't
                         // wait for other stuff first.
                         vector<CInv> vInv;
-                        vInv.push_back(CInv(MSG_BLOCK, hashBestChain));
+                        vInv.push_back(CInv(MSG_BLOCK, chainActive.Tip()->GetBlockHash()));
                         pfrom->PushMessage("inv", vInv);
                         pfrom->hashContinue = 0;
                     }
@@ -3610,7 +3609,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
                 if (!fImporting && !fReindex)
                     pfrom->AskFor(inv);
             } else if (inv.type == MSG_BLOCK && mapOrphanBlocks.count(inv.hash)) {
-                PushGetBlocks(pfrom, pindexBest, GetOrphanRoot(mapOrphanBlocks[inv.hash]));
+                PushGetBlocks(pfrom, chainActive.Tip(), GetOrphanRoot(mapOrphanBlocks[inv.hash]));
             } else if (nInv == nLastBlock) {
                 // In case we are on a very long side-chain, it is possible that we already have
                 // the last block in an inv bundle sent in response to getblocks. Try to detect
@@ -3658,10 +3657,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
 
         // Send the rest of the chain
         if (pindex)
-            pindex = pindex->GetNextInMainChain();
+            pindex = chainActive.Next(pindex);
         int nLimit = 500;
         LogPrint("net", "getblocks %d to %s limit %d\n", (pindex ? pindex->nHeight : -1), hashStop.ToString().c_str(), nLimit);
-        for (; pindex; pindex = pindex->GetNextInMainChain())
+        for (; pindex; pindex = chainActive.Next(pindex))
         {
             if (pindex->GetBlockHash() == hashStop)
             {
@@ -3701,14 +3700,14 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
             // Find the last block the caller has in the main chain
             pindex = locator.GetBlockIndex();
             if (pindex)
-                pindex = pindex->GetNextInMainChain();
+                pindex = chainActive.Next(pindex);
         }
 
         // we must use CBlocks, as CBlockHeaders won't include the 0x00 nTx count at the end
         vector<CBlock> vHeaders;
         int nLimit = 2000;
         LogPrint("net", "getheaders %d to %s\n", (pindex ? pindex->nHeight : -1), hashStop.ToString().c_str());
-        for (; pindex; pindex = pindex->GetNextInMainChain())
+        for (; pindex; pindex = chainActive.Next(pindex))
         {
             vHeaders.push_back(pindex->GetBlockHeader());
             if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop)
@@ -4174,7 +4173,7 @@ bool SendMessages(CNode* pto, bool fSendTrickle)
         // Start block sync
         if (pto->fStartSync && !fImporting && !fReindex) {
             pto->fStartSync = false;
-            PushGetBlocks(pto, pindexBest, uint256(0));
+            PushGetBlocks(pto, chainActive.Tip(), uint256(0));
         }
 
         // Resend wallet transactions that haven't gotten in a block yet
diff --git a/src/main.h b/src/main.h
index 83b0d07f6..46d629044 100644
--- a/src/main.h
+++ b/src/main.h
@@ -74,14 +74,8 @@ extern CScript COINBASE_FLAGS;
 
 extern CCriticalSection cs_main;
 extern std::map<uint256, CBlockIndex*> mapBlockIndex;
-extern std::vector<CBlockIndex*> vBlockIndexByHeight;
 extern std::set<CBlockIndex*, CBlockIndexWorkComparator> setBlockIndexValid;
-extern CBlockIndex* pindexGenesisBlock;
-extern int nBestHeight;
-extern uint256 nBestChainWork;
 extern uint256 nBestInvalidWork;
-extern uint256 hashBestChain;
-extern CBlockIndex* pindexBest;
 extern unsigned int nTransactionsUpdated;
 extern uint64 nLastBlockTx;
 extern uint64 nLastBlockSize;
@@ -153,8 +147,6 @@ void UnloadBlockIndex();
 bool VerifyDB(int nCheckLevel, int nCheckDepth);
 /** Print the loaded block tree */
 void PrintBlockTree();
-/** Find a block by height in the currently-connected chain */
-CBlockIndex* FindBlockByHeight(int nHeight);
 /** Process protocol messages received from a given node */
 bool ProcessMessages(CNode* pfrom);
 /** Send queued protocol messages to be sent to a give node */
@@ -819,15 +811,6 @@ public:
         return (CBigNum(1)<<256) / (bnTarget+1);
     }
 
-    bool IsInMainChain() const
-    {
-        return nHeight < (int)vBlockIndexByHeight.size() && vBlockIndexByHeight[nHeight] == this;
-    }
-
-    CBlockIndex *GetNextInMainChain() const {
-        return nHeight+1 >= (int)vBlockIndexByHeight.size() ? NULL : vBlockIndexByHeight[nHeight+1];
-    }
-
     bool CheckIndex() const
     {
         return CheckProofOfWork(GetBlockHash(), nBits);
@@ -849,17 +832,7 @@ public:
         return pbegin[(pend - pbegin)/2];
     }
 
-    int64 GetMedianTime() const
-    {
-        const CBlockIndex* pindex = this;
-        for (int i = 0; i < nMedianTimeSpan/2; i++)
-        {
-            if (!pindex->GetNextInMainChain())
-                return GetBlockTime();
-            pindex = pindex->GetNextInMainChain();
-        }
-        return pindex->GetMedianTimePast();
-    }
+    int64 GetMedianTime() const;
 
     /**
      * Returns true if there are nRequired or more blocks of minVersion or above
@@ -870,8 +843,8 @@ public:
 
     std::string ToString() const
     {
-        return strprintf("CBlockIndex(pprev=%p, pnext=%p, nHeight=%d, merkle=%s, hashBlock=%s)",
-            pprev, GetNextInMainChain(), nHeight,
+        return strprintf("CBlockIndex(pprev=%p, nHeight=%d, merkle=%s, hashBlock=%s)",
+            pprev, nHeight,
             hashMerkleRoot.ToString().c_str(),
             GetBlockHash().ToString().c_str());
     }
@@ -1011,9 +984,59 @@ public:
     }
 };
 
+/** An in-memory indexed chain of blocks. */
+class CChain {
+private:
+    std::vector<CBlockIndex*> vChain;
 
+public:
+    /** Returns the index entry for the genesis block of this chain, or NULL if none. */
+    CBlockIndex *Genesis() const {
+        return vChain.size() > 0 ? vChain[0] : NULL;
+    }
 
+    /** Returns the index entry for the tip of this chain, or NULL if none. */
+    CBlockIndex *Tip() const {
+        return vChain.size() > 0 ? vChain[vChain.size() - 1] : NULL;
+    }
 
+    /** Returns the index entry at a particular height in this chain, or NULL if no such height exists. */
+    CBlockIndex *operator[](int nHeight) const {
+        if (nHeight < 0 || nHeight >= (int)vChain.size())
+            return NULL;
+        return vChain[nHeight];
+    }
+
+    /** Compare two chains efficiently. */
+    friend bool operator==(const CChain &a, const CChain &b) {
+        return a.vChain.size() == b.vChain.size() &&
+               a.vChain[a.vChain.size() - 1] == b.vChain[b.vChain.size() - 1];
+    }
+
+    /** Efficiently check whether a block is present in this chain. */
+    bool Contains(const CBlockIndex *pindex) const {
+        return (*this)[pindex->nHeight] == pindex;
+    }
+
+    /** Find the successor of a block in this chain, or NULL if the given index is not found or is the tip. */
+    CBlockIndex *Next(const CBlockIndex *pindex) const {
+        if (Contains(pindex))
+            return (*this)[pindex->nHeight + 1];
+        else
+            return NULL;
+    }
+
+    /** Return the maximal height in the chain. Is equal to chain.Tip() ? chain.Tip()->nHeight : -1. */
+    int Height() const {
+        return vChain.size() - 1;
+    }
+
+    /** Set/initialize a chain with a given tip. Returns the forking point. */
+    CBlockIndex *SetTip(CBlockIndex *pindex);
+};
+
+/** The currently-connected chain of blocks. */
+extern CChain chainActive;
 
 
 
diff --git a/src/miner.cpp b/src/miner.cpp
index 30c600071..e9c1d9aff 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -176,7 +176,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
     int64 nFees = 0;
     {
         LOCK2(cs_main, mempool.cs);
-        CBlockIndex* pindexPrev = pindexBest;
+        CBlockIndex* pindexPrev = chainActive.Tip();
         CCoinsViewCache view(*pcoinsTip, true);
 
         // Priority order to process transactions
@@ -467,7 +467,7 @@ bool CheckWork(CBlock* pblock, CWallet& wallet, CReserveKey& reservekey)
     // Found a solution
     {
         LOCK(cs_main);
-        if (pblock->hashPrevBlock != hashBestChain)
+        if (pblock->hashPrevBlock != chainActive.Tip()->GetBlockHash())
             return error("BitcoinMiner : generated block is stale");
 
         // Remove key from key pool
@@ -510,7 +510,7 @@ void static BitcoinMiner(CWallet *pwallet)
         // Create new block
         //
         unsigned int nTransactionsUpdatedLast = nTransactionsUpdated;
-        CBlockIndex* pindexPrev = pindexBest;
+        CBlockIndex* pindexPrev = chainActive.Tip();
 
         auto_ptr<CBlockTemplate> pblocktemplate(CreateNewBlockWithKey(reservekey));
         if (!pblocktemplate.get())
@@ -613,7 +613,7 @@ void static BitcoinMiner(CWallet *pwallet)
                 break;
             if (nTransactionsUpdated != nTransactionsUpdatedLast && GetTime() - nStart > 60)
                 break;
-            if (pindexPrev != pindexBest)
+            if (pindexPrev != chainActive.Tip())
                 break;
 
             // Update nTime every few seconds
diff --git a/src/net.cpp b/src/net.cpp
index 5afedb1fd..5d6f1f46a 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -540,6 +540,8 @@ void CNode::Cleanup()
 
 void CNode::PushVersion()
 {
+    int nBestHeight = g_signals.GetHeight().get_value_or(0);
+
     /// when NTP implemented, change to just nTime = GetAdjustedTime()
     int64 nTime = (fInbound ? GetAdjustedTime() : GetTime());
     CAddress addrYou = (addr.IsRoutable() && !IsProxy(addr) ? addr : CAddress(CService("0.0.0.0",0)));
@@ -1482,6 +1484,8 @@ void static StartSync(const vector<CNode*> &vNodes) {
     CNode *pnodeNewSync = NULL;
     double dBestScore = 0;
 
+    int nBestHeight = g_signals.GetHeight().get_value_or(0);
+
     // Iterate over all nodes
     BOOST_FOREACH(CNode* pnode, vNodes) {
         // check preconditions for allowing a sync
diff --git a/src/net.h b/src/net.h
index b57f38fe3..c4dd2d8a2 100644
--- a/src/net.h
+++ b/src/net.h
@@ -28,7 +28,6 @@ static const unsigned int MAX_INV_SZ = 50000;
 
 class CNode;
 class CBlockIndex;
-extern int nBestHeight;
 
 
 
@@ -52,6 +51,7 @@ void SocketSendData(CNode *pnode);
 // Signals for message handling
 struct CNodeSignals
 {
+    boost::signals2::signal<int ()> GetHeight;
     boost::signals2::signal<bool (CNode*)> ProcessMessages;
     boost::signals2::signal<bool (CNode*, bool)> SendMessages;
 };
diff --git a/src/qt/clientmodel.cpp b/src/qt/clientmodel.cpp
index b33f534f7..af96f11bf 100644
--- a/src/qt/clientmodel.cpp
+++ b/src/qt/clientmodel.cpp
@@ -42,7 +42,7 @@ int ClientModel::getNumConnections() const
 
 int ClientModel::getNumBlocks() const
 {
-    return nBestHeight;
+    return chainActive.Height();
 }
 
 int ClientModel::getNumBlocksAtStartup()
@@ -53,8 +53,8 @@ int ClientModel::getNumBlocksAtStartup()
 
 QDateTime ClientModel::getLastBlockDate() const
 {
-    if (pindexBest)
-        return QDateTime::fromTime_t(pindexBest->GetBlockTime());
+    if (chainActive.Tip())
+        return QDateTime::fromTime_t(chainActive.Tip()->GetBlockTime());
     else if(!isTestNet())
         return QDateTime::fromTime_t(1231006505); // Genesis block's time
     else
@@ -63,7 +63,7 @@ QDateTime ClientModel::getLastBlockDate() const
 
 double ClientModel::getVerificationProgress() const
 {
-    return Checkpoints::GuessVerificationProgress(pindexBest);
+    return Checkpoints::GuessVerificationProgress(chainActive.Tip());
 }
 
 void ClientModel::updateTimer()
diff --git a/src/qt/transactiondesc.cpp b/src/qt/transactiondesc.cpp
index e27aa93a4..93fc8cab2 100644
--- a/src/qt/transactiondesc.cpp
+++ b/src/qt/transactiondesc.cpp
@@ -17,7 +17,7 @@ QString TransactionDesc::FormatTxStatus(const CWalletTx& wtx)
     if (!IsFinalTx(wtx))
     {
         if (wtx.nLockTime < LOCKTIME_THRESHOLD)
-            return tr("Open for %n more block(s)", "", wtx.nLockTime - nBestHeight + 1);
+            return tr("Open for %n more block(s)", "", wtx.nLockTime - chainActive.Height() + 1);
         else
             return tr("Open until %1").arg(GUIUtil::dateTimeStr(wtx.nLockTime));
     }
diff --git a/src/qt/transactionrecord.cpp b/src/qt/transactionrecord.cpp
index ea2c1f0a5..162908a9a 100644
--- a/src/qt/transactionrecord.cpp
+++ b/src/qt/transactionrecord.cpp
@@ -160,14 +160,14 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
         idx);
     status.confirmed = wtx.IsConfirmed();
     status.depth = wtx.GetDepthInMainChain();
-    status.cur_num_blocks = nBestHeight;
+    status.cur_num_blocks = chainActive.Height();
 
     if (!IsFinalTx(wtx))
     {
         if (wtx.nLockTime < LOCKTIME_THRESHOLD)
         {
             status.status = TransactionStatus::OpenUntilBlock;
-            status.open_for = wtx.nLockTime - nBestHeight + 1;
+            status.open_for = wtx.nLockTime - chainActive.Height() + 1;
         }
         else
         {
@@ -221,7 +221,7 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
 
 bool TransactionRecord::statusUpdateNeeded()
 {
-    return status.cur_num_blocks != nBestHeight;
+    return status.cur_num_blocks != chainActive.Height();
 }
 
 QString TransactionRecord::getTxID() const
diff --git a/src/qt/transactiontablemodel.cpp b/src/qt/transactiontablemodel.cpp
index 07f6a6215..6f7a5933a 100644
--- a/src/qt/transactiontablemodel.cpp
+++ b/src/qt/transactiontablemodel.cpp
@@ -250,9 +250,9 @@ void TransactionTableModel::updateTransaction(const QString &hash, int status)
 
 void TransactionTableModel::updateConfirmations()
 {
-    if(nBestHeight != cachedNumBlocks)
+    if(chainActive.Height() != cachedNumBlocks)
     {
-        cachedNumBlocks = nBestHeight;
+        cachedNumBlocks = chainActive.Height();
         // Blocks came in since last poll.
         // Invalidate status (number of confirmations) and (possibly) description
         //  for all rows. Qt is smart enough to only actually request the data for the
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index bda39b675..099fbe8dc 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -73,10 +73,10 @@ void WalletModel::updateStatus()
 
 void WalletModel::pollBalanceChanged()
 {
-    if(nBestHeight != cachedNumBlocks)
+    if(chainActive.Height() != cachedNumBlocks)
     {
         // Balance and number of transactions might have changed
-        cachedNumBlocks = nBestHeight;
+        cachedNumBlocks = chainActive.Height();
         checkBalanceChanged();
     }
 }
diff --git a/src/rpcblockchain.cpp b/src/rpcblockchain.cpp
index 398f33605..957241d6a 100644
--- a/src/rpcblockchain.cpp
+++ b/src/rpcblockchain.cpp
@@ -17,10 +17,10 @@ double GetDifficulty(const CBlockIndex* blockindex)
     // minimum difficulty = 1.0.
     if (blockindex == NULL)
     {
-        if (pindexBest == NULL)
+        if (chainActive.Tip() == NULL)
             return 1.0;
         else
-            blockindex = pindexBest;
+            blockindex = chainActive.Tip();
     }
 
     int nShift = (blockindex->nBits >> 24) & 0xff;
@@ -66,7 +66,7 @@ Object blockToJSON(const CBlock& block, const CBlockIndex* blockindex)
 
     if (blockindex->pprev)
         result.push_back(Pair("previousblockhash", blockindex->pprev->GetBlockHash().GetHex()));
-    CBlockIndex *pnext = blockindex->GetNextInMainChain();
+    CBlockIndex *pnext = chainActive.Next(blockindex);
     if (pnext)
         result.push_back(Pair("nextblockhash", pnext->GetBlockHash().GetHex()));
     return result;
@@ -80,7 +80,7 @@ Value getblockcount(const Array& params, bool fHelp)
             "getblockcount\n"
             "Returns the number of blocks in the longest block chain.");
 
-    return nBestHeight;
+    return chainActive.Height();
 }
 
 Value getbestblockhash(const Array& params, bool fHelp)
@@ -90,7 +90,7 @@ Value getbestblockhash(const Array& params, bool fHelp)
             "getbestblockhash\n"
             "Returns the hash of the best (tip) block in the longest block chain.");
 
-    return hashBestChain.GetHex();
+    return chainActive.Tip()->GetBlockHash().GetHex();
 }
 
 Value getdifficulty(const Array& params, bool fHelp)
@@ -145,11 +145,11 @@ Value getblockhash(const Array& params, bool fHelp)
             "Returns hash of block in best-block-chain at <index>.");
 
     int nHeight = params[0].get_int();
-    if (nHeight < 0 || nHeight > nBestHeight)
+    if (nHeight < 0 || nHeight > chainActive.Height())
         throw runtime_error("Block number out of range.");
 
-    CBlockIndex* pblockindex = FindBlockByHeight(nHeight);
-    return pblockindex->phashBlock->GetHex();
+    CBlockIndex* pblockindex = chainActive[nHeight];
+    return pblockindex->GetBlockHash().GetHex();
 }
 
 Value getblock(const Array& params, bool fHelp)
diff --git a/src/rpcdump.cpp b/src/rpcdump.cpp
index 842910c7e..61cd07d50 100644
--- a/src/rpcdump.cpp
+++ b/src/rpcdump.cpp
@@ -102,7 +102,7 @@ Value importprivkey(const Array& params, bool fHelp)
             throw JSONRPCError(RPC_WALLET_ERROR, "Error adding key to wallet");
 
         if (fRescan) {
-            pwalletMain->ScanForWalletTransactions(pindexGenesisBlock, true);
+            pwalletMain->ScanForWalletTransactions(chainActive.Genesis(), true);
             pwalletMain->ReacceptWalletTransactions();
         }
     }
@@ -124,7 +124,7 @@ Value importwallet(const Array& params, bool fHelp)
     if (!file.is_open())
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
 
-    int64 nTimeBegin = pindexBest->nTime;
+    int64 nTimeBegin = chainActive.Tip()->nTime;
 
     bool fGood = true;
 
@@ -175,11 +175,11 @@ Value importwallet(const Array& params, bool fHelp)
     }
     file.close();
 
-    CBlockIndex *pindex = pindexBest;
+    CBlockIndex *pindex = chainActive.Tip();
     while (pindex && pindex->pprev && pindex->nTime > nTimeBegin - 7200)
         pindex = pindex->pprev;
 
-    LogPrintf("Rescanning last %i blocks\n", pindexBest->nHeight - pindex->nHeight + 1);
+    LogPrintf("Rescanning last %i blocks\n", chainActive.Height() - pindex->nHeight + 1);
     pwalletMain->ScanForWalletTransactions(pindex);
     pwalletMain->ReacceptWalletTransactions();
     pwalletMain->MarkDirty();
@@ -243,8 +243,8 @@ Value dumpwallet(const Array& params, bool fHelp)
     // produce output
     file << strprintf("# Wallet dump created by Bitcoin %s (%s)\n", CLIENT_BUILD.c_str(), CLIENT_DATE.c_str());
     file << strprintf("# * Created on %s\n", EncodeDumpTime(GetTime()).c_str());
-    file << strprintf("# * Best block at time of backup was %i (%s),\n", nBestHeight, hashBestChain.ToString().c_str());
-    file << strprintf("#   mined on %s\n", EncodeDumpTime(pindexBest->nTime).c_str());
+    file << strprintf("# * Best block at time of backup was %i (%s),\n", chainActive.Height(), chainActive.Tip()->GetBlockHash().ToString().c_str());
+    file << strprintf("#   mined on %s\n", EncodeDumpTime(chainActive.Tip()->nTime).c_str());
     file << "\n";
     for (std::vector<std::pair<int64, CKeyID> >::const_iterator it = vKeyBirth.begin(); it != vKeyBirth.end(); it++) {
         const CKeyID &keyid = it->second;
diff --git a/src/rpcmining.cpp b/src/rpcmining.cpp
index b013b4b20..f123c3a9e 100644
--- a/src/rpcmining.cpp
+++ b/src/rpcmining.cpp
@@ -37,10 +37,7 @@ void ShutdownRPCMining()
 // or from the last difficulty change if 'lookup' is nonpositive.
 // If 'height' is nonnegative, compute the estimate at the time when a given block was found.
 Value GetNetworkHashPS(int lookup, int height) {
-    CBlockIndex *pb = pindexBest;
-
-    if (height >= 0 && height < nBestHeight)
-        pb = FindBlockByHeight(height);
+    CBlockIndex *pb = chainActive[height];
 
     if (pb == NULL || !pb->nHeight)
         return 0;
@@ -148,7 +145,7 @@ Value getmininginfo(const Array& params, bool fHelp)
             "Returns an object containing mining-related information.");
 
     Object obj;
-    obj.push_back(Pair("blocks",           (int)nBestHeight));
+    obj.push_back(Pair("blocks",           (int)chainActive.Height()));
     obj.push_back(Pair("currentblocksize", (uint64_t)nLastBlockSize));
     obj.push_back(Pair("currentblocktx",   (uint64_t)nLastBlockTx));
     obj.push_back(Pair("difficulty",       (double)GetDifficulty()));
@@ -192,10 +189,10 @@ Value getwork(const Array& params, bool fHelp)
         static CBlockIndex* pindexPrev;
         static int64 nStart;
         static CBlockTemplate* pblocktemplate;
-        if (pindexPrev != pindexBest ||
+        if (pindexPrev != chainActive.Tip() ||
             (nTransactionsUpdated != nTransactionsUpdatedLast && GetTime() - nStart > 60))
         {
-            if (pindexPrev != pindexBest)
+            if (pindexPrev != chainActive.Tip())
             {
                 // Deallocate old blocks since they're obsolete now
                 mapNewBlock.clear();
@@ -209,7 +206,7 @@ Value getwork(const Array& params, bool fHelp)
 
             // Store the pindexBest used before CreateNewBlock, to avoid races
             nTransactionsUpdatedLast = nTransactionsUpdated;
-            CBlockIndex* pindexPrevNew = pindexBest;
+            CBlockIndex* pindexPrevNew = chainActive.Tip();
             nStart = GetTime();
 
             // Create new block
@@ -328,7 +325,7 @@ Value getblocktemplate(const Array& params, bool fHelp)
     static CBlockIndex* pindexPrev;
     static int64 nStart;
     static CBlockTemplate* pblocktemplate;
-    if (pindexPrev != pindexBest ||
+    if (pindexPrev != chainActive.Tip() ||
         (nTransactionsUpdated != nTransactionsUpdatedLast && GetTime() - nStart > 5))
     {
         // Clear pindexPrev so future calls make a new block, despite any failures from here on
@@ -336,7 +333,7 @@ Value getblocktemplate(const Array& params, bool fHelp)
 
         // Store the pindexBest used before CreateNewBlock, to avoid races
         nTransactionsUpdatedLast = nTransactionsUpdated;
-        CBlockIndex* pindexPrevNew = pindexBest;
+        CBlockIndex* pindexPrevNew = chainActive.Tip();
         nStart = GetTime();
 
         // Create new block
diff --git a/src/rpcrawtransaction.cpp b/src/rpcrawtransaction.cpp
index fcc5359dd..5384b6590 100644
--- a/src/rpcrawtransaction.cpp
+++ b/src/rpcrawtransaction.cpp
@@ -87,9 +87,9 @@ void TxToJSON(const CTransaction& tx, const uint256 hashBlock, Object& entry)
         if (mi != mapBlockIndex.end() && (*mi).second)
         {
             CBlockIndex* pindex = (*mi).second;
-            if (pindex->IsInMainChain())
+            if (chainActive.Contains(pindex))
             {
-                entry.push_back(Pair("confirmations", 1 + nBestHeight - pindex->nHeight));
+                entry.push_back(Pair("confirmations", 1 + chainActive.Height() - pindex->nHeight));
                 entry.push_back(Pair("time", (boost::int64_t)pindex->nTime));
                 entry.push_back(Pair("blocktime", (boost::int64_t)pindex->nTime));
             }
diff --git a/src/rpcwallet.cpp b/src/rpcwallet.cpp
index cafb6db9b..433cc8b73 100644
--- a/src/rpcwallet.cpp
+++ b/src/rpcwallet.cpp
@@ -76,7 +76,7 @@ Value getinfo(const Array& params, bool fHelp)
         obj.push_back(Pair("walletversion", pwalletMain->GetVersion()));
         obj.push_back(Pair("balance",       ValueFromAmount(pwalletMain->GetBalance())));
     }
-    obj.push_back(Pair("blocks",        (int)nBestHeight));
+    obj.push_back(Pair("blocks",        (int)chainActive.Height()));
     obj.push_back(Pair("timeoffset",    (boost::int64_t)GetTimeOffset()));
     obj.push_back(Pair("connections",   (int)vNodes.size()));
     obj.push_back(Pair("proxy",         (proxy.first.IsValid() ? proxy.first.ToStringIPPort() : string())));
@@ -1180,7 +1180,7 @@ Value listsinceblock(const Array& params, bool fHelp)
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter");
     }
 
-    int depth = pindex ? (1 + nBestHeight - pindex->nHeight) : -1;
+    int depth = pindex ? (1 + chainActive.Height() - pindex->nHeight) : -1;
 
     Array transactions;
 
@@ -1192,23 +1192,8 @@ Value listsinceblock(const Array& params, bool fHelp)
             ListTransactions(tx, "*", 0, true, transactions);
     }
 
-    uint256 lastblock;
-
-    if (target_confirms == 1)
-    {
-        lastblock = hashBestChain;
-    }
-    else
-    {
-        int target_height = pindexBest->nHeight + 1 - target_confirms;
-
-        CBlockIndex *block;
-        for (block = pindexBest;
-             block && block->nHeight > target_height;
-             block = block->pprev)  { }
-
-        lastblock = block ? block->GetBlockHash() : 0;
-    }
+    CBlockIndex *pblockLast = chainActive[chainActive.Height() + 1 - target_confirms];
+    uint256 lastblock = pblockLast ? pblockLast->GetBlockHash() : 0;
 
     Object ret;
     ret.push_back(Pair("transactions", transactions));
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index eeeacb0ad..67165760b 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -65,10 +65,10 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     {
         CBlock *pblock = &pblocktemplate->block; // pointer for convenience
         pblock->nVersion = 1;
-        pblock->nTime = pindexBest->GetMedianTimePast()+1;
+        pblock->nTime = chainActive.Tip()->GetMedianTimePast()+1;
         pblock->vtx[0].vin[0].scriptSig = CScript();
         pblock->vtx[0].vin[0].scriptSig.push_back(blockinfo[i].extranonce);
-        pblock->vtx[0].vin[0].scriptSig.push_back(pindexBest->nHeight);
+        pblock->vtx[0].vin[0].scriptSig.push_back(chainActive.Height());
         pblock->vtx[0].vout[0].scriptPubKey = CScript();
         if (txFirst.size() < 2)
             txFirst.push_back(new CTransaction(pblock->vtx[0]));
@@ -193,14 +193,14 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     mempool.clear();
 
     // subsidy changing
-    int nHeight = pindexBest->nHeight;
-    pindexBest->nHeight = 209999;
+    int nHeight = chainActive.Height();
+    chainActive.Tip()->nHeight = 209999;
     BOOST_CHECK(pblocktemplate = CreateNewBlockWithKey(reservekey));
     delete pblocktemplate;
-    pindexBest->nHeight = 210000;
+    chainActive.Tip()->nHeight = 210000;
     BOOST_CHECK(pblocktemplate = CreateNewBlockWithKey(reservekey));
     delete pblocktemplate;
-    pindexBest->nHeight = nHeight;
+    chainActive.Tip()->nHeight = nHeight;
 
     BOOST_FOREACH(CTransaction *tx, txFirst)
         delete tx;
diff --git a/src/txdb.cpp b/src/txdb.cpp
index 0d2fdc288..24ee8ec3e 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -223,10 +223,6 @@ bool CBlockTreeDB::LoadBlockIndexGuts()
                 pindexNew->nStatus        = diskindex.nStatus;
                 pindexNew->nTx            = diskindex.nTx;
 
-                // Watch for genesis block
-                if (pindexGenesisBlock == NULL && diskindex.GetBlockHash() == Params().HashGenesisBlock())
-                    pindexGenesisBlock = pindexNew;
-
                 if (!pindexNew->CheckIndex())
                     return error("LoadBlockIndex() : CheckIndex failed: %s", pindexNew->ToString().c_str());
 
diff --git a/src/wallet.cpp b/src/wallet.cpp
index 26ffc71e1..0f0ce7e63 100644
--- a/src/wallet.cpp
+++ b/src/wallet.cpp
@@ -799,7 +799,7 @@ int CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, bool fUpdate)
             // no need to read and scan block, if block was created before
             // our wallet birthday (as adjusted for block time variability)
             if (nTimeFirstKey && (pindex->nTime < (nTimeFirstKey - 7200))) {
-                pindex = pindex->GetNextInMainChain();
+                pindex = chainActive.Next(pindex);
                 continue;
             }
 
@@ -810,7 +810,7 @@ int CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, bool fUpdate)
                 if (AddToWalletIfInvolvingMe(tx.GetHash(), tx, &block, fUpdate))
                     ret++;
             }
-            pindex = pindex->GetNextInMainChain();
+            pindex = chainActive.Next(pindex);
         }
     }
     return ret;
@@ -864,7 +864,7 @@ void CWallet::ReacceptWalletTransactions()
         if (fMissing)
         {
             // TODO: optimize this to scan just part of the block chain?
-            if (ScanForWalletTransactions(pindexGenesisBlock))
+            if (ScanForWalletTransactions(chainActive.Genesis()))
                 fRepeat = true;  // Found missing transactions: re-do re-accept.
         }
     }
@@ -1933,7 +1933,7 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64> &mapKeyBirth) const {
             mapKeyBirth[it->first] = it->second.nCreateTime;
 
     // map in which we'll infer heights of other keys
-    CBlockIndex *pindexMax = FindBlockByHeight(std::max(0, nBestHeight - 144)); // the tip can be reorganised; use a 144-block safety margin
+    CBlockIndex *pindexMax = chainActive[std::max(0, chainActive.Height() - 144)]; // the tip can be reorganised; use a 144-block safety margin
     std::map<CKeyID, CBlockIndex*> mapKeyFirstBlock;
     std::set<CKeyID> setKeys;
     GetKeys(setKeys);
@@ -1953,7 +1953,7 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64> &mapKeyBirth) const {
         // iterate over all wallet transactions...
         const CWalletTx &wtx = (*it).second;
         std::map<uint256, CBlockIndex*>::const_iterator blit = mapBlockIndex.find(wtx.hashBlock);
-        if (blit != mapBlockIndex.end() && blit->second->IsInMainChain()) {
+        if (blit != mapBlockIndex.end() && chainActive.Contains(blit->second)) {
             // ... which are already in a block
             int nHeight = blit->second->nHeight;
             BOOST_FOREACH(const CTxOut &txout, wtx.vout) {