diff --git a/src/init.cpp b/src/init.cpp
index 8cbf21cc4..a2e77b423 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -227,6 +227,7 @@ bool AppInit2(int argc, char* argv[])
             "  -rpcport=<port>  \t\t  " + _("Listen for JSON-RPC connections on <port> (default: 8332)") + "\n" +
             "  -rpcallowip=<ip> \t\t  " + _("Allow JSON-RPC connections from specified IP address") + "\n" +
             "  -rpcconnect=<ip> \t  "   + _("Send commands to node running on <ip> (default: 127.0.0.1)") + "\n" +
+            "  -blocknotify=<cmd> "     + _("Execute command when the best block changes (%s in cmd is replaced by block hash)") + "\n" +
             "  -keypool=<n>     \t  "   + _("Set key pool size to <n> (default: 100)") + "\n" +
             "  -rescan          \t  "   + _("Rescan the block chain for missing wallet transactions") + "\n";
 
diff --git a/src/main.cpp b/src/main.cpp
index 15f047bf7..52a3c3fde 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -7,6 +7,7 @@
 #include "db.h"
 #include "net.h"
 #include "init.h"
+#include <boost/algorithm/string/replace.hpp>
 #include <boost/filesystem.hpp>
 #include <boost/filesystem/fstream.hpp>
 
@@ -1278,6 +1279,14 @@ bool static Reorganize(CTxDB& txdb, CBlockIndex* pindexNew)
 }
 
 
+static void
+runCommand(std::string strCommand)
+{
+    int nErr = ::system(strCommand.c_str());
+    if (nErr)
+        printf("runCommand error: system(%s) returned %d\n", strCommand.c_str(), nErr);
+}
+
 bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
 {
     uint256 hash = GetHash();
@@ -1321,7 +1330,8 @@ bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
     }
 
     // Update best block in wallet (so we can detect restored wallets)
-    if (!IsInitialBlockDownload())
+    bool fIsInitialDownload = IsInitialBlockDownload();
+    if (!fIsInitialDownload)
     {
         const CBlockLocator locator(pindexNew);
         ::SetBestChain(locator);
@@ -1336,6 +1346,14 @@ bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
     nTransactionsUpdated++;
     printf("SetBestChain: new best=%s  height=%d  work=%s\n", hashBestChain.ToString().substr(0,20).c_str(), nBestHeight, bnBestChainWork.ToString().c_str());
 
+    std::string strCmd = GetArg("-blocknotify", "");
+
+    if (!fIsInitialDownload && !strCmd.empty())
+    {
+        boost::replace_all(strCmd, "%s", hashBestChain.GetHex());
+        boost::thread t(runCommand, strCmd); // thread runs free
+    }
+
     return true;
 }