Measured the frequency of socioeconomically disadvantaged preschool children's aggressive, assertive, and submissive behaviors in play interaction with their mothers. Boys were significantly more assertive but not more aggressive or submissive than girls. Sociofamilial predictors including maternal depression, maternal anger, parenting stress, family life stress, and maternal perceptions of children's aggressive behavior were examined. Sex of the child interacted with (a) maternal depression to predict aggressive and assertive behavior and (b) maternal anger to predict submissive behavior. In all cases where child's sex exerted a significant moderating influence, boys' behavior was more vulnerable to differences in levels of maternal depression and anger, with lower rates of boys' behavior associated with higher levels of maternal distress.