Adolescents who experience homelessness are at higher risk for abusing substances, and for being exposed to substance-using peers. The current study used a longitudinal design to track substance abuse, affiliation with substance-using peers, and episodes of homelessness among a sample of 223 adolescents who were housed at the baseline data collection and 148 adolescents who were housed at baseline. Participants were interviewed at six waves over 6.5 years, covering an age range from 13 to 25. Many participants experienced a recurrence of homelessness during follow-up, with 64.6% of the baseline homeless group and 22.6% of the baseline housed group reporting an additional episode of homelessness. Both alcohol abuse and other drug abuse symptoms showed an increase in adolescence followed by slowing in early adulthood. Recent homelessness and friend alcohol use predicted alcohol abuse symptoms, and the strength of the influence of friend use decreased over time. Recent homelessness and friend drug use predicted other drug abuse symptoms. Duration of the initial episode of adolescent homelessness showed no influence on substance abuse over time, or the effects of other predictors, highlighting the importance of conceptualizing the experience of homelessness as a recent stressor rather than an enduring personal characteristic (Authors).