Data were collected in spring 1988 by means of anonymous self-report questionnaires completed in classrooms. Results revealed that students who use illicit drugs display deficits in school performance, quality of family relationships, and health and increased psychological symptoms. Compared with nonusers, they are more delinquent and more actively involved with their peers and live in social settings in which the perceived use of drugs by other adolescents and parents is more extensive. Juvenile delinquency and the extent of perceived drug use consistently increase with each higher stage of drug use. Crack users have the lowest level of psychosocial functioning of any drug-using group. Findings indicated that despite declines over the last 2 decades in the prevalence of the use of different drugs, youth who use drugs display characteristics over historical time similar to those of young drug users 20 years ago. Tables and 28 references (Author abstract modified)