Scanning force microscopic images of cytochrome c oxidase immobilized within an electrode-supported lipid bilayer membrane are reported. These images represent the first direct evidence that the microscopic architecture of this important model system effectively mimics the microstructure proposed for the inner mitochondrial membrane. The images reveal (1) that the oxidase is present as monomers and small aggregates within the supported membrane and (2) that the oxidase constitutes similar to 20% of the lipid bilayer membrane. The latter finding allows an estimation of the lower limit for the minimum turnover rate (similar to 0.5 electrons/s) required for the transition of the oxidase from its resting to pulsed kinetic state.