diff --git a/asyncqueue.h b/asyncqueue.h
index e847c685..d9223979 100644
--- a/asyncqueue.h
+++ b/asyncqueue.h
@@ -31,6 +31,10 @@ int AsyncUnitCreate(const char* queueName, pAsyncUnit* unit);
  * \param port number or service name on the target host 
  * \param unit pointer to the AsyncUnit created on positive return
  * \return positive if successful
+ *
+ * If <port> is null then <host> points to an existing queue name.
+ * If a queue exists for <host>/<port>, then that queue is used.
+ * If neither of the above hold, a new queue is created.
  */
 int AsyncUnitCreateHost(const char* host,
     const char* port,