1. A method for prioritizing fetching of instructions in a multithreaded processor system, comprising: determining a first metric for each thread of a plurality of threads executing on said multithreaded processor system based on the number of instructions currently buffered for execution on that thread; determining a second metric for each thread respectively based on at least one execution parameter for that thread; determining a ranked priority order for the threads from the first and second metrics; and fetching an instruction for the thread with the highest determined priority in the ranked priority order from a source of instructions.