The relationship among after-school time, parental monitoring, and problem behavior was examined in a sample of 1,170 early adolescents. Those spending unsupervised time with peers reported higher levels of aggression, delinquency, substance use, and susceptibility to peer pressure, and lower levels of parental monitoring, than did adolescents at home with parents. Adolescents home alone after school were similar to those who spent time with adults or in school activities.