This is a longitudinal follow-up study of men and women in their middle and late twenties who had been participants in an intensive, four-year, longitudinal study during their adolescence and youth. Over 600 participants are involved; 432 had been in junior-senior high school during the years of the earlier study, and 205 had been in college. On the basis of four, successive annual questionnaires, a large amount of developmental information was collected in the areas of alcohol use and drug use, of sexual behavior, and of general deviance, and also in the areas of personality and social environmental factors relevant to such behavior. The research was guided by and served to test a social-psychological theory of problem behavior in youth. The assessments again cover personality, the social environment, and behavior, with intensive concern for alcohol and drug use, problems associated with that use, attiudes toward alcohol and drugs, and the availability of both. The research should make clear whether alcohol and drug use in young adulthood are signalled by and predictable from personality and behavior during adolescence and youth.