Bovine cytochrome c oxidase has been successfully immobilized in an electrode-supported lipid bilayer membrane. The surface confined oxidase is capable of directly transferring electrons to the underlying electrode making characterization of the enzyme with direct electrochemical methods facile. Cyclic voltammetry indicates that the immobilized oxidase is capable of transferring electrons to the solid electrode over a wide range of pH and temperature values. Furthermore, the oxidase maintains its electron transfer properties at temperatures in excess of 80 degrees C. Upon cooling the electrode back to room temperature, it was found that the enzyme still retained its electron transfer capabilities revealing the robust nature of the enzyme is this environment. In addition the oxidase continues to be capable of mediating electron transfer from solution-resident, reduce cytochrome c to the underlying metal electrode. The use of oxidase-modified electrodes enables the detection of solutions of reduced cytochrome c at concentrations as low as 0.25 mu M.