This experimental study examined the influence of a classwide peer-tutoring reading program (Peer-Assisted Learning Strategies; PALS) on the quality of social relationships of elementary school children. Using a sociometric procedure, social preference and friendships were evaluated before and after the PALS program. Overall (mean) and differential (conditional on pre-treatment status) effects were considered. Modest positive effects were detected, but only for children who were unpopular or had no friends before the intervention. We discuss the possibility that problem behaviors may negate the generally positive effects of peer-mediated activity on social relations. (Contains 2 tables and 1 figure.)