The effect of benzyl alcohol, benzaldehyde and benzoic acid on the production of extracellular hydrogen peroxide (H2O2) by the ligninolytic fungus Pleurotus eryngii was investigated. It was found that an equilibrium between oxidative and reductive reactions of these compounds is established, leading to the continuous production of H2O2. A multienzymatic cyclic system is proposed in which H2O2 is produced extracellularly by the action of aryl-alcohol oxidase on benzyl alcohol, the most abundant compound after redox reactions, and to a lower extent on benzaldehyde. The oxidation products of these reactions, bezaldehyde and benzoic acid, are reduced by intracellular dehydrogenases.