The presence of atypical liver alcohol dehydrogenase (ADH) was determined in samples of liver tissue from 222 alcoholic and nonalcoholic subjects to determine its prevalence in the Spanish population, and to evaluate the possible relationship between the presence of this isoenzyme and the development of alcoholism and alcoholic liver disease. Alcoholic patients were classified into the following groups: control subjects, with normal liver pathology (group 1), patients with noncirrhotic liver disease (group 2), and patients with cirrhosis of the liver (group 3). Nonalcoholic subjects were also divided, following the same criteria, into groups 4, 5, and 6, respectively. The prevalence of atypical ADH in the population analyzed was 16.2%. Atypical ADH was present in 14.9% of alcoholics and in 17.4% of nonalcoholics (p = NS). There were no significant differences when the prevalence of atypical ADH of alcoholic and nonalcoholic patients with similar degrees of liver pathology was compared (group 1 vs. 4, group 2 vs. 5, and group 3 vs. 6). The prevalence of atypical ADH was also similar in cirrhotic patients with respect to those of noncirrhotic liver disease and control patients, either in alcoholic or nonalcoholic groups. Our findings indicate that the prevalence of atypical ADH in the Spanish population is similar to that reported for other Caucasian groups. Moreover, the presence of atypical ADH does not play a role in the development of alcoholism nor in the development of alcoholic liver disease in the population analyzed.