gamma-Glutamyltranspeptidase (gamma GT) appears in serum in multiple forms; their significance and clinical utility in hepatobiliary and pancreatic diseases are still a matter of controversy. Electrophoretic separation of the multiple forms of gamma GT on agarose gel was performed in 20 alcoholic patients (six with cirrhosis and 14 with fatty liver) and the results compared with those obtained in 50 healthy volunteers, 43 patients affected with chronic hepatitis C, 36 patients with posthepatitic cirrhosis and in 52 epileptic patients on long-term anti-epileptic medication. Multiple forms of gamma GT were separated into several bands (up to 11), labelled 0a, 0b, 1a, 1b, 2a, 2b, 2c, 3a, 3b, 4a, 4b. In the alcoholic patients nine fractions were detected, and the electrophoretic pattern observed was significantly different from that observed in healthy volunteers and in patients with chronic hepatitis C or posthepatitic cirrhosis. No differences were observed in the electrophoretic patterns in the alcohol abusers and epileptic patients. In alcoholic patients significant differences were observed in the electrophoretic patterns in relation to the degree of liver injury; the electrophoretic patterns in patients with alcohol-related cirrhosis and posthepatitic cirrhosis differed significantly. The separation of multiple forms of gamma GT has high sensitivity and good reproducibility. It may be proposed as a complementary test in the diagnosis of alcoholic liver disease.