A phenomenological model describing the transfer of lysozyme between a bulk aqueous phase and a reversed micellar phase in a stirred membrane cell has been confirmed. Transport of the enzyme at the interface at low surfactant concentrations is dominant, while that through the membrane is the rate-determining step at high surfactant concentrations. Complete separation of alpha-chymotrypsin from lysozyme using a supported liquid membrane filled with reversed micelles demonstrates the feasibility of the present process for enzyme separation.