The effort by developmental psychopathologists to understand the etiology of antisocial behavior has resulted in several significant findings. First, aggressive behavior is highly stable from early childhood into adolescence and adulthood. Second, parental factors including rearing practices and parental psychopathology, are correlated with childhood behavior problems. It was the aim of the present study to examine the correlates and stability of aggressive behavior in a sample of toddlers from low income families. Eight-nine mother-child dyads (52 boys and 37 girls) were observed in laboratory assessments when the child was 18- and 24-months old. Frequency and pervasiveness of aggression were coded from videotapes. Familial criminality, maternal depressive symptomatology, child noncompliance, and difficult child temperament were examined as contributors to the prediction of aggression in toddlers. Stability of aggression was moderate, especially for aggression occurring in low-stress situations. While there were few sex differences in the frequency and stability of aggression, there were marked differences in the correlates and predictors of aggression. Gender-specific, interactional models of the development of aggression are proposed.