xv, 83 p. A print copy of this title is available through the UO Libraries. Search the library catalog for the location and call number. / Peer influences on adolescence substance use have been widely demonstrated. In particular, social interactions that are centered around and reinforcing of antisocial values, known as deviant peer contagion, are predictive of a variety of antisocial outcomes, including substance use. However, much less is known about the interpersonal dynamics between friends that are associated with resilience to peer contagion. Recent work has associated self-regulation with resilience to the effects of associating with deviant and substance-using peers. Limited resource models of self-regulation have proposed that social interactions may tax regulatory resources to the point that self-regulation becomes impaired. Youth with more limited regulatory resources may demonstrate increased susceptibility to influence from peers. However, in friendship interactions, self-regulatory behaviors are highly dependent on the self-regulation of the partner. Therefore, the present study examined dyadic regulation in friendship interactions consistent with the idea of a dyadic process. In addition to investigating the construct validity of dyadic regulation, it was hypothesized that dyadic regulation would moderate the impact of peer contagion on problematic substance use. Furthermore, consistent with a limited resource model, it was predicted that adolescents with declining dyadic regulation over the course of an interaction would be more susceptible to peer contagion. Problematic substance use and interaction patterns within friendships were assessed in a sample of 711 (355 male, 356 female) ethnically diverse 16- and 17-year-old adolescents. Using videotaped observations of friendship interactions, dyadic regulation was assessed by rating responsiveness, self-focused intrusions, attention, and conversational turn-taking. Deviant peer contagion was assessed through the proportion of the interaction spent discussing deviant topics. Contrary to the hypothesized self-regulatory resilience model, those dyads that were more highly regulated while discussing deviant topics demonstrated the highest levels of problematic tobacco use. Consistent with a limited resource model of regulation, however, dyads with decreasing regulation over the course of an interaction appeared to be the most vulnerable to deviant peer contagion, demonstrating greater problematic marijuana use. These results are encouraging of further investigation in this area and may have implications for direct interventions targeting risk for substance use as well as reducing iatrogenic effects in group interventions. / Adviser: Thomas J. Dishion