Liver Function Test (LFT) abnormalities are frequently observed in narcotic addicts. However, the role of alcohol in producing such changes remains unclear. In order to evaluate the effects of alcohol in producing LFT elevations as well as the use of routine LFTs to serve as biochemical markers for alcoholism in narcotic addicts, 612 addicts participating in a randomized control trial of intervention in alcoholism were studied. Baseline parameters including LFTs and history of alcohol use were obtained on entry into the study and subsequently periodically during follow-up which varied from 6 months to 2 years (mean 13.5 months). On entry to the study, 104 of 612 (17%) of addicts were classified as alcoholics. Mean values of LFTs (SGOT, SGPT, Alkaline phosphatase, GGTP) in the alcoholic cohort were significantly increased compared to those among nonalcoholics (p<0.01 to<0.001 for individual tests). Mean values of LFTs did not significantly change during methadone maintenance in either group. Although a greater proportion of alcoholic addicts had elevated LFTs, the predictive values for each test (18 to 35%) were sufficiently low to prevent them from being used as biochemical markers of alcoholism. These findings suggest that although elevations in LFTs are frequently present in narcotic addicts and are significantly greater among addicts who are also alcoholic, most elevations are not specifically due to alcohol. Conventional LFTs are therefore of limited value in assessing alcoholism among narcotic addicts.