We examined the value of laboratory markers of excessive alcohol (ethanol) intake as predictors of mortality, morbidity, and health-care utilization in a cohort of 330 patients attending an acute ambulatory care service. Among men, all four markers examined--gamma-glutamyltransferase (GGT) and aspartate aminotransferase (AST) activities, high-density lipoprotein cholesterol (HDL-C), and mean corpuscular volume (MCV)--were predictive of medical sequelae and health-care utilization over a 3-year period. In contrast, social problems were more closely related to the amount of alcohol consumption at initial assessment than to any biological marker. Serum GGT and AST activities and MCV were predictive of medical sequelae in women. The predictive value of GGT was an independent risk factor and did not merely reflect recent alcohol intake or the presence of chronic liver disease. We conclude that these readily available laboratory tests provide important prognostic information and should be an integral part of the assessment of persons with hazardous alcohol consumption.