The activity of γ-glutamyl transferase (γ-GT) in the liver of 36 chronic alcoholics was twice as high as in the control group. The elevation was of the same order in cases with and without hepatic lesions. However, the activity of γ-GT in the sera of alcoholic patients with chronic hepatitis and liver cirrhosis was significantly higher than in the remaining alcoholics. There was no correlation between the enzyme activities in the liver and in the serum of the patients examined. Consequently, the determination of liver γ-GT activity bears no clinical significance in chronic alcoholics.