A method and apparatus are provided for executing instructions of a multi-threaded processor having multiple hardware threads (32, 34) with differing hardware resources comprising the steps of receiving a plurality of streams of instructions (38, 44) and determining which hardware threads are able to receive instructions for execution (40, 46), determining whether a thread determined to be available for executing an instructions has the hardware resources available required by that instructions (36) and executing the instruction in dependence on the result of the determination (50).