An array of closely spaced interdigitated microelectrodes was applied to the sensitive detection of reversible redox couples. The measurement is based on the redox cyclization between the adjacent microband electrodes of the interdigitated array (IDA), when both the respective oxidation and reduction potential are applied at the electrode pairs. The multiple oxidation and reduction result in an increased generation of current. The steady-state current of mediators, such as phenazine methosulfate, hexacyanoferrate(II), pyrocatechol, benzoquinone and p-aminophenol, was amplified by a factor of 10–20 compared with the current of single electrodes. The high collection efficiency enabled this signal amplification rate to be obtained. The detection limit for p-aminophenol was 100 nmol l–1. The IDA sensor was applied to the determination of alkaline phosphatase and β-galactosidase activity by detecting enzymatically generated p-aminophenol.