Simultaneous amperometric determination of two phenolic compounds was performed by using a tyrosinase (TYR) electrode and a TYR-peroxidase (POD) bienzyme electrode on the basis of differences in the selectivities for two phenolic compounds between the two enzyme electrodes. Catechol and p-cresol contained in the same solution were determined simultaneously with the present system. The response of the bienzyme electrode was greater than the sum of the response of the TYR electrode and that of a POD electrode. This amplification effect may be responsible for the differences in the selectivities. Amplification mechanisms were also discussed. (C) 2004 Elsevier B.V. All rights reserved.