A stable monolayer of alcohol dehydrogenase (ADH) enzyme has been prepared by spreading an aqueous solution of ADH on a water subphase containing stearic acid monolayer. This ADH-stearic acid monolayer has been successfully transferred onto a conducting polypyrrole-coated glass electrode by the Langmuir-Blodgett (LB) technique. ADH catalyses the reaction between the coenzyme beta-NAD + (beta form of oxidized nicotinamide adenine dinucleotide) and ethanol to produce NADH and acetaldehyde. Conducting polypyrrole acts as a mediator for transferring electrons produced on NADH oxidation. This LB-immobilized polypyrrole-mediated enzyme electrode can be used as an ethanol sensor. It shows better sensitivity than sensors consisting of ADH immobilized by chemical cross-linking with glutaraldehyde. This LB sensor can be used for low ethanol concentration (in the micro-molar range).