Rotating disc voltammetry data for the reaction of myoglobin, a model “enzyme” in a thin lipid film, with ferredoxin was shown to fit the Michaelis–Menten kinetic model, but did not fit a simple linear EC’ model. Advantages of this thin-film method are a lipid bilayer environment similar to that of membrane bound enzymes, the tiny amounts of proteins required, and simplicity of instrumentation compared to alternative methodology. The apparent K M for ferredoxin reduction by reduced myoglobin was 112μM, k cat was 102s −1 , and k cat /K M was 9.1×10 4 M −1 s −1 indicating relatively fast kinetics. Results suggest that this method should be amenable to kinetic studies of enzymes in lipid films with protein reaction partners in solution.