An overview of key findings in the trend analysis shows differences in illicit drug use between college and non-college respondents for specific drugs, as well as male-female differences in illicit drug use. Similar data are provided for trends in alcohol use. Data on trends in cigarette smoking cover age and cohort-related differences, college-non-college differences, and male-female differences. Trend data also encompass racial/ethnic comparisons and drug use in the eighth grade. Trend findings indicate that from the late 1970's to the early 1990's there were appreciable declines in the use of several illicit drugs among 12th-grade students and even larger declines in their use among college students and young adults. A chapter on study design and procedures address the surveys of high school seniors, surveys of lower grades, and follow-up surveys of seniors. Four chapters that focus on young adults post-high school cover the prevalence of drug use in early and middle adulthood, trends in drug use in early and middle adulthood, attitudes and beliefs about drugs among young adults, and the social milieu for young adults. Two chapters on college students focus on the prevalence of drug use in this population and trends in drug use. 30 tables and 65 figures