Findings from this study were drawn from a larger research project entitled, "Seattle Homeless Adolescent Research Project" (SHARP). SHARP aimed to provide a better understanding of the background characteristics and mental health status of homeless youth and to assess the effectiveness of various types of case management with these youth. The data for the current study were collected during face-to-face interviews with approximately 200 youth; because individual participants may have skipped 1 or more interviews over the course of the study, the number for individual analyses ranged from 121 to 194. All variables examined were measured through a self-administered booklet that focused on delinquent and aggressive behavior, antisocial behavior, and the level of alcohol and drug use. The relationship between measures of substance use and delinquency at each quarterly interview was examined by using a two-step structural equations modeling approach. The findings indicate that although substance use and delinquency were highly correlated in the sample, they were separate and identifiable constructs. Further, an individual's level of delinquency at the first quarterly interview was associated with change in substance use up to 6 months later. Initial level of substance use, however, did not apparently have a significant impact on subsequent delinquent behavior. The findings support the hypothesis that engaging in delinquent acts makes an adolescent more likely to use alcohol and drugs. These results challenge the common practice of making sobriety a requirement for participating in drug and alcohol treatment, given that adolescent substance use may, in fact, lag behind other problematic behaviors. Interventions that target the delinquent behaviors and the social context in which they are likely to occur should have a significant impact on future alcohol and drug use. 4 tables and 42 references