Stability and Variability of Adolescents’ Affiliation with Delinquent Friends: Predictors and Consequences Mara Brendgen, University of Montreal, Montreal, Canada, Frank Vitaro, University of Montreal, Canada and William M. Bukowski, Concordia University, Montreal, Canada Abstract The effects of stability versus change in adolescents’affiliation with delinquent or non- delinquent friends over a two-year period (T1–T2) on delinquent behavior one year later (T3) were examined. In addition, T1 predictors of stability and change in the affiliation with delinquent or nondelinquent friends from T1 to T2 were assessed. Par- ticipants were 152 adolescents (77 girls, mean age 12.1 years at T1). Friends’delin- quent behavior was assessed through friends’self-reports. The T1 predictor variables included adolescents’ own delinquent behavior, attitude toward delinquent behavior, and parental monitoring. Adolescents’ friendship affiliations at T2, but not at T1, pre- dicted delinquent behavior at T3, suggesting a recency effect of friendship affiliation. Attitude toward delinquent behavior at T1 was the main predictor of stability versus change in adolescents’ affiliation with delinquent or nondelinquent friends from T1 to T2. Keywords: Friendship; Stability; Delinquency The Social Interactional Model (e.g., Dishion, Capaldi, Spracklen, & Li, 1995; Dishion, Patterson, Stoolmiller, & Skinner, 1991; Patterson, Reid, & Dishion, 1992) suggests that, in addition to parents, peers play a crucial role in the development of delinquent behavior. Specifically, maladaptive parenting practices are believed to foster antisocial behaviors and attitudes in the child which, in turn, may lead to the affiliation with delinquent friends. Through social learning mechanisms, delinquent friends are then assumed to be an additional expedient on the path toward delinquency by providing the youngster with the opportunity to further learn, practice, and refine antisocial and delinquent behaviors. Notably, most empirical studies have focused on delinquent friendship affiliation at only one point in time (e.g., Agnew, 1991; Dishion et al., 1991; Dishion et al., 1995; Elliott, Huizinga, & Ageton, 1985; Farrington, 1991; Keenan, Loeber, Zhang, Stouthamer-Loeber, & van Kammen, 1995; Simons, Wu, © Blackwell Publishers Ltd. 2000. Published by Blackwell Publishers, 108 Cowley Road, Oxford OX4 1JF, UK and 350 Main Street, Malden, MA 02148, USA. Correspondance referring to this article should be addressed to Mara Brendgen, University of Montreal, Research Unit on Children’s Psychosocial Maladjustment, 3050 Edouard-Montpetit Blvd., Montreal, Quebec, H3T 1J7, Canada.