This chapter reviews contemporary research on children’s gender development. Theories addressing cultural and social-structural, cognitive and motivational, and biological influences are summarized. These theoretical frameworks are used to interpret gender-related variations in the following areas: temperament, gender schemas, self-concepts, sexist attitudes, gender segregation and peer group relations, play, sports, academic achievement, communication style, direct and indirect aggression, sexual harassment, and friendship intimacy. Gender similarities and within-gender variability are emphasized.