The four reaction parameters-pH, reaction temperature, molar ratio (R) of water to surfactant, and Aerosol-OT concentration-have significant linear, quadratic, and interactive effects on the initial rate and the degree of hydrolysis for lipase-mediated hydrolysis of triacyl-glycerols (TAG) in Aerosol-OT/iso-octane reverse micellar media. Reaction temperature and pH had the most significant influence on the rate and the degree of hydrolysis, whereas Aerosol-OT concentration had the least influence on those parameters. The initial rate was most influenced by the interactive effect of pH with all other variables, whereas the degree of hydrolysis was the most influenced by the interactive effect of reaction temperature with other variables. Lower-level variable combinations were favorable over higher-level variable combinations to TAG hydrolysis in reverse micellar media. Regression models, developed for the initial rate and the degree of hydrolysis as a function of reaction variables, accounted for up to 96% of the variation in the two responses. The optimum reaction condition ranges were determined based on maximization of both the rate and the degree of hydrolysis. The differences in the physicochemical characteristics of substrates had no significant effect on the optimum condition ranges. However, the noticeable differences were observed for these ranges between the systems with Rhizopus javanicus and Candida cylindracea lipases. Lipase-catalyzed hydrolysis of TAG in Aerosol-OT/iso-octane reverse micellar media was optimum at about 22 degrees C, 140 mM Aerosol-OT concentration, pH 6.8, and R value of 14.