The report includes a description of the surveys and a panel-study feature that permits the analysis of change over time in the same individuals as they enter adulthood. Procedures described include the sampling plans and field procedures used in both the annual in-school cross-sectional surveys of the 8th-, 10th-, and 12th-grade students and the follow-up surveys into early and middle adulthood. Related methodological issues such as response rates, population coverage, and the validity of the measures are also discussed. Key findings are presented across the five populations included in the surveys. Generally, trends in overall illicit substance use among American college students have paralleled those of age peers not in college. The use of most such drugs declined substantially sometime after 1980, with differences observed in cohort effects, notably an increase in high school seniors' use of a number of drugs, but no such increase among college students and young adults. Separate chapters cover the prevalence of drug use in early and middle adulthood, trends in drug use in this age period, attitudes and beliefs about drugs among young adults, the social milieu for young adults, the prevalence of drug use among college students, and trends in drug use among college students. In addition to data on overall drug use, tables show trends in the use of a range of specific illegal substances and the use of alcohol and tobacco products. Extensive tables and figures and a subject index