Gender segregation continues to exist in many activity and occupational domains. This article uses the expectancy effect perspective to analyze the role parents may play in influencing their children to engage in gender role stereotyped activities. It outlines the theoretical bases for such effects, and discusses how to distinguish between accuracy and perceptual bias in parents' gender role differentiated perceptions of their children's competencies and interests. Then it summarizes the results of a series of studies, which show that parents distort their perceptions of their own children in gender role stereotypic activities such as math and sports, that the child's gender affects parents' causal attributions for their children's performance in gender role stereotypic activities, and that these perceptual biases influence the children's own self-perceptions and activity choices. Finally, the article presents a theoretical model of how these processes may occur.