This study used direct observation to examine how a history of exposure to interparental aggression relates to children's behavior during conflict with both parents present. Ninety 2-parent families with a child 9-13 years of age participated. Consistent with a sensitization hypothesis, results indicated that exposure to interparental physical aggression during the previous year was related to child withdrawal, anxiety, and distraction during a family discussion task. In addition, the interaction between reported interparental aggression and observed child-directed hostility accounted for significant variance in boys' behavior. Follow-up correlation analyses revealed that boys who had been exposed to physical marital aggression were more anxious and distracting when their parents were more hostile toward them during the discussion, whereas boys who had not been exposed withdrew more.