A theoretical model of adolescent drug use is developed which integrates propositions derived from social control and differential association theories. The path model includes parental attachment, religious attachment, educational attachment, conventional values, and drug-using friends as precursors of drug use. For a sample of 2,626 adolescents from the southwestern United States, the model explains 34 percent of the variation in self-reported lifetime alcohol use, 27 percent in lifetime cigarette use, 42 percent in lifetime marijuana use, 26 percent in lifetime use of amphetamines and depressants, and 50 percent in overall lifetime drug use. The best single predictor of drug use is association with drug-using friends. The processes leading to involvement with drugs appear to be very similar across drug types. Adolescent drug use is widespread in America. Numerous recent authors suggest that involvement in such behavior has become a national concern, whether the substance is tobacco (Grunberg and Baum 1984; Humble et al. 1985; Lichtenstein 1982), alcohol (Barnes 1984; Pandina et al. 1984; Wechsler et al. 1984), marijuana (Hendin et al. 1981; Smith et al. 1982; Smith 1984), or other drugs (McDermott 1984; Marcos and Bahr 1985; Weidman 1983). Macdonald (1984) refers to adolescent drug use as a national disaster because of the high proportion of adolescents who use drugs and the negative consequences associated with use. By the time they are seniors in high school, over 90 percent of American adolescents have tried alcohol *Paper presented at the 1985 meeting of the Pacific Sociological Association. We acknowledge the cooperation of the schools that participated in this project, particularly the students who completed the questionnaires. We are grateful to Grant Rose and Tom Martin for computer assistance, to two anonymous referees for their suggestions, and to Norene Petersen and Brenda Johnson for clerical assistance. Address correspondence to Anastasios C. Marcos, Department of Sociology, 800 SWKT, Brigham Young University, Provo, UT 84602.