Progress in the area of faradaic bioelectrochemistry over the last decade has been reviewed. Electrochemical and spectroscopic studies of the protein-electrode interface are discussed along with the use of electron transfer promoters, self-assembled monolayers (SAMs), and surfactant films. Voltammetric techniques are described that permit rapid, in-situ measurement of formal potentials while also providing kinetic resolution on the sub-millisecond time scale. Some enzymes, especially those of analytical interest, must be coupled or 'wired' to the electrode using mediators in order to achieve rapid electron transfer. Supramolecular structures designed to facilitate electron transfer and to immobilize co-factors are described. The use of electrochemically-based biosensors for in-vivo measurements is documented. (C) 3000 Elsevier Science Ltd. All rights reserved.