The liquid hydrocarbon/water interface with immobilized amphiphilic catalysts can serve as the simplest model of biological membrane convenient for the investigation of redox reaction accompanied by spatial separation of charges. In this review, we have described the vectorial redox reactions at oil/water interfaces. The structure of liquid interfaces, donor-acceptor interactions in the electrical double layer, specific bounding between molecules plays the dominant role in interfacial catalysis. Theoretical aspects of charge transfer reactions at oil/water interfaces are discussed. The activation energy of electron transfer depends on the charges of the reactants and dielectric permittivity of the non-aqueous phase. Experimental interfacial catalytic systems are described. Amphiphilic molecules were studied as catalysts of electron transfer reactions at the oil/water interface. A concerted 2:1:l-electron mechanism for cytochrome oxidase functioning is evaluated by thermodynamic and kinetic analysis. The conditions are formulated for the occurrence of multielectron oxygen reduction. Kharkats and Volkov first presented proofs that cytochrome c oxidase reduces molecular oxygen by synchronous multielectron mechanism without O-2(-) intermediate formation [Yu.I. Kharkats, A.G. Volkov, Biochim. Biophys. Acta 891 (1987) 56]. As the field progresses after this pioneering observation, it became clear that the first step of dioxygen reduction is two-electron concerted process. As follows from thermodynamics energy for the Hf-pump functioning is liberated only at the last two steps of water formation on addition of third and fourth electrons independently of the reaction pathway. (C) 1998 Elsevier Science Ltd. All rights reserved.