A model linking children's perceptions of adults' gender stereotypes about mathematics and science ability, children's stereotypes, and children's perceptions of their own mathematics and science competence was tested in 302 fourth, sixth, and eighth graders. When boys believed that adults hold more traditional stereotypes, they tended to hold corresponding beliefs that girls are relatively less capable or that boys are more capable in mathematics and science. These group competence ratings, in turn, were related to self-perceptions of ability for sixth- and eighth-grade boys. In contrast, most paths were nonsignificant for girls. The results provided support for both social status theory and experiential theory. We discuss implications regarding the influence of stereotypes on motivation and identity development. (Contains 3 figures and 1 table.)