Fifty-nine persons, 23 chronic alcoholics and 36 normal healthy persons with a well described alcohol consumption, had the serum concentration of alpha-fetoprotein determined by a sensitive monoclonal immunofluorescent assay. A significant elevation in S-AFP was found in alcoholics, median 4.1 kIU/1 as compared to 3.0kIU/l in near-abstainers (<12g ethanol per day) (p<0.02). This difference was not explained by differences in age. S-AFP correlated positively with age (p = 0.01). In non-alcoholics a borderline significant correlation with S-AFP was found with average daily alcohol consumption (self-reported) (p = 0.09) and a significant correlation with the serum concentration of carbohydrate-deficient transferrin (S-CDT) (p = 0.004). In 11 alcoholics 2 months of abstention from alcohol was accompanied by a median reduction of 21% in S-AFP (p < 10^-5). In alcoholics, but not in social drinkers, S-AFP correlated with S-ASAT (p = 0.004). The increase of S-AFP with alcohol consumption may reflect reversible alcohol-induced liver affection.