The most common causes of referral to child mental health services are childhood behavior problems involving misconduct, aggression and non-compliance. Children with early problems in these areas are at risk for later social-emotional problems and psychiatric disorders. The purpose of this research is to identify in the first years of life, characteristics of children that predict problem behaviors at school age, especially problems with aggression. Forty-eight two-year-old children of depressed and well mothers were observed and assessed on multiple occasions, using naturalistic and experimental procedures. They were seen again at ages five and six. Preliminary analyses indicated strong patterns of continuity over time in problems with aggression, particularly in children with depressed mothers. Children who were out-of-control and intensely aggressive toward playmates at age two were seen as aggressive with playmates and described by their parents as antisocial at ages five and six. Observed social competence at age five could be predicted from earlier skills in modulating emotions in social relationships (e.g., using positive emotions as a means to initiate and maintain interactions).