ABSTRACT The serum concentration of bilirubin and the activities of aspartate aminotransferase (ASAT, GOT), alanine aminotransferase (ALAT, GPT), γ-glutamyltransferase (GT), total amylase and pancreatic isoamylase have been determined in serum of 182 male chronic alcoholics. Twelve per cent had abnormally high levels of bilirubin, 73% increased activity of S-ASAT, 50% increased S-ALAT, and 69% increased S-GT. The highest values were often found after 5–20 years of well documented alcoholism. Some patients with alcoholism of more than 20 years' duration displayed a slight tendency towards normalization of the activities. For all parameters the scatter around the mean was greater in the patients than in the controls. Patients who had had attacks of delirium showed slightly higher S-ASAT and S-ALAT than other alcoholics. Determination of S-ALAT and S-bilirubin did not add to the cases with abnormal laboratory tests demonstrated by the combination of S-ASAT and S-GT. In 14 patients the above mentioned parameters were within normal limits, even though severe alcoholism had lasted for many years. Isoamylase determination disclosed 20% to have decreased activity of pancreatic isoamylases in serum, whereas only 6% had low total serum amylase activity.