Mushroom tyrosinase and glucose dehydrogenase from Acinetobacter calcoaceticus were immobilized in poly(vinyl)alcohol membranes and coupled with a Clark-type oxygen electrode to give a substrate (analyte) regenerating cycle for monitoring of nanomolar concentrations of phenolic compounds. In this way the response for catechol, phenol, p-cresol, p-chlorophenol and p-acetamidophenol was amplified by a factor of 450, 300, 240, 150, and 140, respectively. The resulting detection limit for catechol and phenol is 0.6 nmol dm(-3) and 0.9 nmol dm(-3), respectively. The measuring linear range for phenol obtained by the amplified electrode extends from 1 to 400 nmol dm(-3). The comparison with the chemical (ascorbic acid) regeneration of the phenolic compounds demonstrates the efficiency of the enzymatic procedure. The biosensor can be used for monitoring of phenolic compounds in environmental or industrial samples.