Youths were initially tested at ages 12, 15, or 18 and retested at ages 15, 18, and 21. The results provide modest support for a common cause model of the drug-crime relationship. While a number of predictor variables drawn from control theory and differential association theory were related to both behaviors, those drawn from the psychological literature on correlates of adolescence deviance tended to be more strongly related to subsequent serious substance use than to serious delinquency. The findings suggest that there is a degree of etiological independence in serious adolescent substance abuse and serious forms of delinquency. Further, while peer behaviors and attitudes were consistent in their effects, school and personality variables differed in their significance as predictors of each target behavior, and significant differences existed across age groups. 6 tables and 56 references. (Author abstract modified)