Due to slow kinetics of electron transfer, dioxygen is reduced at a platinum cathode several hundred millivolts negative of its formal potential, Biological catalysts, in combination with redox mediators, have the potential to circumvent the overpotential for the direct electroreduction of dioxygen to water. This payer describes how the redox mediator, 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate), is used to reduce dioxygen to water using the fungal enzyme, laccase, as the catalyst for homogeneous electron transfer and the results obtained when this chemistry is used in the cathode compartment of a biofuel cell.