The author examined Michigan Alcohol Screening Test (MAST) scores and selected laboratory results of 50 patients encountered in a family physician's office. The severity of alcohol-related problems (as reflected by the MAST) was compared to the toxic effects of alcohol (as measured by the SGOT, γ-glutamyltransferase levels, and the mean cell volume). No association was found between the MAST scores and the cellular toxic effect of alcohol. Patients with extensive alcohol-related problems were more likely to report prolonged sobriety. These results suggest that testing with both MAST and laboratory tests is required to discover the effects of alcohol abuse in ambulatory patients.