diff --git a/src/libCom/logClient/iocLog.c b/src/libCom/logClient/iocLog.c
index c6c707c30..e62da2050 100644
--- a/src/libCom/logClient/iocLog.c
+++ b/src/libCom/logClient/iocLog.c
@@ -18,7 +18,6 @@
 
 #define epicsExportSharedSymbols
 #include "envDefs.h"
-#include "errlog.h"
 #include "logClient.h"
 #include "iocLog.h"
 
@@ -90,9 +89,6 @@ static logClientId iocLogClientInit (void)
         return NULL;
     }
     id = logClientCreate (addr, port);
-    if (id != NULL) {
-        errlogAddListener ( logClientSendMessage, id );
-    }
     return id;
 }
 
@@ -139,13 +135,3 @@ logClientId epicsShareAPI logClientInit (void)
 {
     return iocLogClientInit ();
 }
-
-/* 
- * logClientSendMessage (); deprecated
- */
-void logClientSendMessage ( logClientId id, const char * message )
-{
-    if ( !iocLogDisable ) {
-        logClientSend (id, message);
-    }
-}
diff --git a/src/libCom/logClient/logClient.c b/src/libCom/logClient/logClient.c
index 4f5daaab1..99ee671d9 100644
--- a/src/libCom/logClient/logClient.c
+++ b/src/libCom/logClient/logClient.c
@@ -24,6 +24,8 @@
 #define epicsExportSharedSymbols
 #include "dbDefs.h"
 #include "epicsEvent.h"
+#include "iocLog.h"
+#include "errlog.h"
 #include "epicsMutex.h"
 #include "epicsThread.h"
 #include "epicsTime.h"
@@ -54,6 +56,11 @@ static const double      LOG_RESTART_DELAY = 5.0; /* sec */
 static const double      LOG_SERVER_CREATE_CONNECT_SYNC_TIMEOUT = 5.0; /* sec */
 static const double      LOG_SERVER_SHUTDOWN_TIMEOUT = 30.0; /* sec */
 
+/*
+ * If set using iocLogPrefix() this string is prepended to all log messages:
+ */
+static char* logClientPrefix = NULL;
+
 /*
  * logClientClose ()
  */
@@ -147,6 +154,8 @@ static void logClientDestroy (logClientId id)
         return;
     }
 
+    errlogRemoveListeners ( logClientSendMessage, (void *) pClient );
+
     logClientClose ( pClient );
 
     epicsMutexDestroy ( pClient->mutex );
@@ -156,22 +165,13 @@ static void logClientDestroy (logClientId id)
     free ( pClient );
 }
 
-/* 
- * logClientSend ()
+/*
+ * This method requires the pClient->mutex be owned already.
  */
-void epicsShareAPI logClientSend ( logClientId id, const char * message )
-{
-    logClient * pClient = ( logClient * ) id;
+static void sendMessageChunk(logClient * pClient, const char * message) {
     unsigned strSize;
 
-    if ( ! pClient || ! message ) {
-        return;
-    }
-
     strSize = strlen ( message );
-
-    epicsMutexMustLock ( pClient->mutex );
-
     while ( strSize ) {
         unsigned msgBufBytesLeft = 
             sizeof ( pClient->msgBuf ) - pClient->nextMsgIndex;
@@ -228,10 +228,31 @@ void epicsShareAPI logClientSend ( logClientId id, const char * message )
             break;
         }
     }
-    
+}
+
+
+/* 
+ * logClientSend ()
+ */
+void epicsShareAPI logClientSend ( logClientId id, const char * message )
+{
+    logClient * pClient = ( logClient * ) id;
+
+    if ( ! pClient || ! message ) {
+        return;
+    }
+
+    epicsMutexMustLock ( pClient->mutex );
+
+    if (logClientPrefix) {
+        sendMessageChunk(pClient, logClientPrefix);
+    }
+    sendMessageChunk(pClient, message);
+
     epicsMutexUnlock (pClient->mutex);
 }
 
+
 void epicsShareAPI logClientFlush ( logClientId id )
 {
     logClient * pClient = ( logClient * ) id;
@@ -528,6 +549,8 @@ logClientId epicsShareAPI logClientCreate (
             pClient->name, LOG_SERVER_CREATE_CONNECT_SYNC_TIMEOUT );
     }
         
+    errlogAddListener ( logClientSendMessage, (void *) pClient );
+
     return (void *) pClient;
 }
 
@@ -550,5 +573,46 @@ void epicsShareAPI logClientShow (logClientId id, unsigned level)
             pClient->sock==INVALID_SOCKET?"INVALID":"OK",
             pClient->connectCount);
     }
+
+    if (logClientPrefix) {
+        printf ("log client: prefix is \"%s\"\n", logClientPrefix);
+    }
 }
 
+/*
+ * logClientSendMessage (); deprecated
+ */
+void logClientSendMessage ( logClientId id, const char * message )
+{
+    if ( !iocLogDisable ) {
+        logClientSend (id, message);
+    }
+}
+
+/*
+ * iocLogPrefix()
+ */
+void epicsShareAPI iocLogPrefix(const char * prefix)
+{
+
+    /* If we have already established a log prefix, don't let the user change
+     * it.  The iocLogPrefix command is expected to be run from the IOC startup
+     * script during initialization; the prefix can't be changed once it has
+     * been set.
+     */
+
+    if (logClientPrefix) {
+        printf ("iocLogPrefix: The prefix was already set to \"%s\" "
+            "and can't be changed.\n", logClientPrefix);
+        return;
+    }
+
+    if (prefix) {
+        unsigned prefixLen = strlen(prefix);
+        if (prefixLen > 0) {
+            char * localCopy = malloc(prefixLen+1);
+            strcpy(localCopy, prefix);
+            logClientPrefix = localCopy;
+        }
+    }
+}
diff --git a/src/libCom/logClient/logClient.h b/src/libCom/logClient/logClient.h
index 8f1ec09d5..1797bbb20 100644
--- a/src/libCom/logClient/logClient.h
+++ b/src/libCom/logClient/logClient.h
@@ -33,6 +33,7 @@ epicsShareFunc logClientId epicsShareAPI logClientCreate (
 epicsShareFunc void epicsShareAPI logClientSend (logClientId id, const char *message);
 epicsShareFunc void epicsShareAPI logClientShow (logClientId id, unsigned level);
 epicsShareFunc void epicsShareAPI logClientFlush (logClientId id);
+epicsShareFunc void epicsShareAPI iocLogPrefix(const char* prefix);
 
 /* deprecated interface; retained for backward compatibility */
 /* note: implementations are in iocLog.c, not logClient.c */