A biomimetic system of cytochrome P450, constituted by [5-(4-(I-methylpyridinium))-10,15,20-triphenylporphyrinato] manganese(III) dichloride (Mn1) included in cetylpyridinium chloride (CPyCl) micellar phase, features good catalytic activity in the NaClO promoted epoxidation of styrene. A closely related system, i.e. [5-(4-(3-trimethylammonium) propyloxyphenyl)-10,15,20-tryphenyl-porphyrinato] manganese(ID) dichloride (Mn2) in cetyltrimethylammonium bromide (CTAB), presents a lower reactivity, similar to that achieved in ethanol-water solvent mixture. A crossover experiment, i.e. that carried out with Mn1/CTAB system, shows intermediate degree of conversion. These findings indicate that the catalytic properties of the investigated systems are deeply influenced by the specific non-covalent interactions established among the catalyst, substrate, and surfactant. (C) 2002 Elsevier Science B.V. All rights reserved.