V. parahaemolyticus possessed an extracellular alkaline protease activity during the stationary growth phase. Various factors such as nitrogen sources, the concentration of NaCl and metal ions were investigated for optimizing the production of alkaline protease from V. parahaemolyticus ATCC 17802. Among the nitrogen sources tested skim milk showed the distinct increase of the activity and the activity was the highest at 2% in final concentration after 60 hours incubation. The addition of NaCl and metal ions did not increase the alkaline protease activity. CoC1₂, CuC1₂, and HgCl rather highly inhibited alkaline protease production.