Children's use of dispositionalattributions to predict the behavior of classmates was studied. Kindergartners, fourth graders, and eighth graders predicted behavior in four situations for classmates who they claimed were (a) smart, (b) not smart, (c) nice, and (d) not nice. They also rated their own and their classmates' current and future relative academic and social comppetence. The results suggest that children as young as kindergarten age predict peer'sbehavior on the basis of dispositionalattributions. However, the youngest children'sattributions were not well differentiated; they predicted that the classmate to whom they gave a positive trait label would perform better than the classmate to whom they gave a negative label in all situations, including situations irrelevant to the label. Predictions became more differentiated with age. All children expected their peers' performance and behavior to be somewhat stable over a period of 1 year, but the older children expected greater stability than the younger children.