A recycling bienzyme electrode for determination of nanomolar ferrocene concentration was developed. The electrode consists of a laccase – glucose dehydrogenase bienzyme membrane coupled with an oxygen electrode. Laccase catalyzes the oxidation of ferrocene with oxygen. Oxidized ferrocene is an electron acceptor for the reaction of glucose oxidation catalyzed by glucose dehydrogenase. The cyclic process of oxidation/reduction of ferrocene gives substrate recycling. The detection is achieved by measuring the decrease in oxygen concentration. In this system the detection limit for ferroceneacetic acid was 0.2 nM.