This article studies the relationships between acculturation and drinking and alcohol-related problems among people of Mexican descent in Mexico and the United States. Subjects in the United States were part of a national probability sample of the Hispanic household population 18 years of age and older. Subjects in Mexico were randomly selected from among adult residents of the city of Morelia and an adjoining rural county, Tarimbaro, both in the State of Michoacan. Both samples were interviewed using the same questionnaire. Response rates were 72% in the United States and 92% in Mexico. Results show that Mexican-American men drink more frequently than men in Michoacan, who, as a group, drink infrequently but consume more often five or more drinks at a sitting as compared with Mexican Americans. Mexican-American women have a lower rate of abstention and a higher rate of women who drink at least once a week and who consume five drinks at a sitting at least once a year than do women in Michoacan. Among men, changes in drinking seem to occur soon after coming to the United States--often within 5 years. Among women, drinking patterns are not related to length of residence in the United States. In spite of less drinking, respondents in Michoacan report more alcohol problems than do Mexican Americans.