Three aspects of young children's social cognition--accurate encoding of social cues, hostile attributions and response access/generation--were assessed among 128 children (64 girls) attending three-, four-, and five-year-old classrooms (ages ranged from 36 to 73 months). Hostile attributions and the quality of strategy generation were both significantly associated with teacher-rated peer competence and aggressiveness, even when children's receptive vocabulary scores and age were controlled. For girls, hostile attributions, but not cue encoding or response generation, was associated with teacher ratings of competence and aggression. For boys, hostile attributions were associated with teacher ratings of competence, and response generation was associated with teacher ratings of competence and aggression. Regression analysis, controlling for sex, age and receptive vocabulary, revealed that both hostile attributions and the quality of social strategy generation, but not encoding of cues, made unique, significant contributions to the prediction of teacher ratings of competence and aggression. (Contains 6 tables.)