Provided are a method, apparatus and a computer program for managing message queues. Message streaming is enabled in a transactional messaging system that supports priority ordering of messages, without the need for complex locking mechanisms. Any messages which are transferred from a message queue to a message consumer after the message consumer initiates commit processing are replaced on the message queue at an appropriate position ahead of other messages. As part of commit processing, the consumer sends back to the manager of the message queue an identification of messages delivered to it before the commit, and this list of messages is extracted and compared with a message log to identify undelivered messages. Successfully delivered and committed messages can be committed by the queue manager, and undelivered messages can be replaced on the queue. A special high priority is assigned to the replaced messages to place them ahead of other messages.