Cytochrome c was found to undergo electron transfer reactions at a gold electrode modified with a Langmuir-Blodgett monolayer of 20-mercaptoeicosane-1-ol/dioleoyl-L-α- phosphatidylcholine (molar ratio, 1/20). The stability of the monolayer and the adsorption behavior of cytochrome c to the monolayer was also examined.