We report simple fermentation conditions for high-level extracellular production of alpha-lytic protease and its mutants by recombinant E. coil. Although transcription was controlled by the lac promoter, addition of the inducer isopropyl-beta-thiogalactopyranoside (IPTG) was generally found to reduce the expression of active protease. We also describe the effects of other factors on the levels of enzyme found in the culture medium.