Blood acetate concentration of 51 intoxicated patients was measured and compared to conventional laboratory markers of chronic alcoholism. Mean blood acetate concentration of 23 chronic alcoholics and 17 heavy drinkers was stgrtrftcarrtty (p < 0.0005) higher than that of 53 nonalcoholic volunteers or 11 occasional drinkers. Blood acetate level was completely independent of blood ethanol concentration ranging from 0.20 to 2.90 promiNe. Blood acetate was elevated in 65% of both chronic alcoholics and heavy drinkers. Gammaghita‐myttransferase was abnormal only in 35%, aspartate aminotransferase in 21% and mean corpuscular volume in 12% of heavy drinkers. Combination (acetate + gammaglutamyttransferase) correctly detected 87% of alcoholics and 71% of heavy drinkers. During ethanol oxidation the upper normal limit of blood acetate is 0.75 mn The specificity of increased blood acetate is as high as 92%. Increased blood acetate is indicative for metabolic tolerance to alcohol and it may be so far the most sensitive and specific laboratory marker of chronic alcoholism and heavy drinking.