Activities of alcohol, aldehyde dehydrogenases (ADH, A1DH, respectively) and gamma-glutamyl transferase (GGT) were estimated in blood serum of patients with Stages I-III alcoholism (54 men) on admission to the hospital, within 1 hr after ethanol testing (in a dose of 0.4 g/kg of body mass) and during the treatment course. Distinct activation of ADH and GGT and decrease in activity of A1DH were found in the patients as compared with healthy volunteers. Alcohol test did not alter noticeably the enzymatic activity studied. The activity of ADH and GGT was normalized in patients with Stages I-II alcoholism during the treatment course. A1DH exhibited the highest diagnostic efficacy, whose sensitivity and specificity were 92% and 84%, respectively; those for ADH 74% and 86% and for GGT 44% and 90%, respectively. Simultaneous estimation of the activity of the three enzymes improved the sensitivity and efficacy of diagnostic technique and enabled the test to be used as an additional criterion in the diagnosis of alcoholism and in the evaluation of the patients' state and therapeutical efficacy.