Groups of patients suffering alcoholism and narcomania were examined for the effect of intoxication on the blood serum enzymes of mainly liver origin: alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), as well as on thymol test. It has been shown that in patients with the first stage of alcoholism one could observe only functional disturbances in the liver: the increase of ADH activity which evidences for the induction of its synthesis. In patients with the first stage of opium narcomania one can record total hyperenzymenia, decrease of de-Rimis coefficient at the expense of more considerable increase of ALT activity than that of AST, as well as the sharp increase of thymol test – these are the signs of destructive and metabolic disturbances in the liver. In patients with the second stage of alcoholism one can observe the decrease of ALDH activity under the increase of ADH, AST, ALT activity and high thymol test-these are the signs of toxical hepatitis. Destructive and metabolic changes increase in the liver in the patients with the second stage of narcomania.