Examined whether features of preschool children's mutual friendships were associated with prosocial and aggressive behavior. Teacher reports of friendship features showed moderate interrater reliability and were associated with teacher reports of aggression and prosocial behavior, and with peer reports of acceptance and rejection. Friendship support related to prosocial behavior. Friendship conflict related to overt aggression and peer rejection. Friendship exclusivity/intimacy related positively to relational aggression, negatively to peer acceptance. (Author/KB)