Interpersonal dynamics within friendships were observed in a sample of 120 (60 male, 60 female) ethnically diverse 16- and 17-year-old adolescents characterized as persistently antisocial, adolescent-onset, and normative. Dyadic mutuality and deviant talk were coded from videotaped friendship interactions. Persistently antisocial adolescents demonstrated lower levels of dyadic mutuality compared with adolescent-onset and normative adolescents. Persistently antisocial and adolescent-onset adolescents spent more time in deviant talk than did normative adolescents. Across groups, girls were rated as more mutual and coded less in deviant talk than boys. Furthermore, friendship dyads who engaged in high levels of deviant talk and were mutual in their interactions reported the highest rates of antisocial behavior.