We have developed a new method of lipase activation for interesterification, in which lipase, in contact with a hydrocarbon-water interface, has been found to have high interesterification activity in an anhydrous solvent. We have applied this activation method to various lipase and obtained high synthetic activity in n-hexane, and have investigated the effect of various hydrocarbon-water interfaces on the synthetic and hydrolytic activities of lipases. The esterification and/or interesterification activity of lipases tested was improved by this activation method, using an n-tetradecane-water interface. From the initial group of lipases, three representative lipases (from Rhizopus japonicus, Chromobacterium viscosum and porcine pancreas) were selected for further study. The effect of various hydrocarbon-water interfaces on synthetic (interesterification or esterification) activity was studied. We demonstrated that the resulting synthetic activity was affected by the choice of hydrocarbon-water interface and that there were differences in the effects of interfaces on the synthetic activity of these lipases.