Production of natural flavour esters by lipase was studied. Lipase can catalyze ester formation when an organic solvent, capable of extracting the ester, is used as a bulk phase solvent. Candida cylindracea lipase, which shows broad substrate specificity and pH stability, was immobilized by adsorption to silica gel. Synthesis of ethyl butyrate was studied as a model. The immobilized lipase was shaken in n-heptane containing ethanol and butyric acid. Ester production rate was optimal around: pH 4, decreasing at higher pH values; 30°C, decreasing at higher temperatures; substrate concentration of 0.4 M ethanol and 0.25 M butyric acid. Enzyme hydration was found necessary for stable activity in repeated use. A variety of flavour esters was produced. Ethyl butyrate production was also evaluated in a packed column of immobilized lipase through which a solution of hexane containing substrate was recycled. With a solution volume to packed bed ratio of 3:1, a space velocity of 20h-1 was found to maximize ethyl butyrate production.