This study examined the stability of adolescent drug use into young adulthood and explored the possible influence of personality on adolescent and adult drug use. Participants in this longitudinal study (N = 640) completed questionnaires which assessed multiple indicators for latent constructs of tobacco, alcohol, cannabis, and hard drugs, and also for the personality constructs of Socialization. In addition, the effects of obedience and extraversion were examined. Results showed that a general drug use factor in adolescence significantly predicted young adult drug use. A particular effect of adolescent obedience on adult drug use was noted. Within adolescence, obedience, extraversion, and the construct of Socialization were significant predictors of drug use. Early onset of smoking predicted adolescent drug use. The implications of these findings for early drug use education and intervention are discussed. Additional analysis explored the possibility of treating obedience as another indicator of Socialization. This model could not provide as good a fit as the original model. The measure of obedience acted as a better predictor of drug use than an overall factor of Socialization. Gender differences are discussed.