This study examined the utility of Cloninger's tridimensional personality theory (1986, 1987a) in predicting preferred substance of abuse and self-reported motivations for use among a sample of 200 adolescent substance abusers and 200 matched community control adolescents. Two primary hypotheses were tested: (1) Cloninger's type II profile is more strongly associated with stimulant use, and his type I profile is more strongly associated with substances having sedative-hypnotic effects; and 2) type II individuals will report motivations for use that focus primarily on obtaining positive rewards, whereas type I individuals will report motivations primarily concerning negative reinforcement or the avoidance of problems and negative life experiences. Our results did not show strong associations between Cloninger's Harm Avoidance and Reward Dependence dimensions and preferred substance or motivations for use. However, in partial support of the hypotheses examined here, we did find that individuals low in novelty seeking (NS) tended to prefer alcohol and marijuana, whereas those high in NS endorsed a wider range of preferred substances. High NS was associated with significantly greater stimulant use and motivations focused on obtaining positive rewards, whereas low NS was associated with greater sedative use and motivations related to avoiding negative emotions or negative life experiences.