The differential amperometric method provides an inexpensive, easily automated method for measuring urine or whole blood alcohol concentrations. The method had the additional advantage of cycling NADH produced which prevents the reaction from coming to equilibrium. The reagent can be made several days prior to use since the diaphorase, NAD** plus , and DCPIP are stable in solution at 0-5 C for up to 1 month. The differential amperometric method has high sensitivity, is specific for ethanol, and can be successfully applied to routine analysis for samples of 10 to 20 mu l.