Until now, most results reported for parallelism in production systems (rule-based systems) have been simulationresults -- very few real parallel implementations exist. In this paper, we present results from our parallelimplementation of OPS5 on the Encore multiprocessor. The implementation exploits very fine-grained parallelismto achieve significant speed-ups. For one of the applications, we achieve 12.4 fold speed-up using 13 processes.Our implementation is also distinct from other parallel implementations in that we parallelize a highly optimizedC-based implementation of OPS5. Running on a uniprocessor, our C-based implementation is 10-20 times fasterthan the standard lisp implementation distributed by Carnegie Mellon University. In addition to presenting theperformance numbers, the paper discusses the amount of contention observed for shared data structures, and thetechniques used to reduce such contention.