Polyphenoloxidase entrapped in Brij 96-cyclohexame reverse micelles showed both cresolase activity towards monophenols and catecholase activity towards diphenols. The kinetic parameters, such as apparent K,,,, temperature effect and pH profile, were determined for catecholase activity, the findings being very close to those found in aqueous systems. The enzyme activity was dependent on the molecular ratio of water to surfactant (o,), obtaining a maximum activity at o, = IO. The stability of the system with time increased with the water content until W, = 10, and then decreased. An inverse relation was found between activity and water volume fraction (6)