Ethanol was determined by reaction with NAD in the presence of alcohol dehydrogenase in a continuous flow system. NADH produced was allowed to react with hexacyanoferrate (III) in the presence of diapharase. The concentration of the produced hexacyanoferrate (II) was monitored biamperometrically using open tubular carbon electrodes. A level of 1.5 × 102mg/100 ml ethanol was detected, with an average precision of 4% relative standard deviation. The ethanol level in blood samples was determined, obtaining a 0.08 correlation coefficient with gas chromatography results.