Several aspects of gender concept development were investigated in 60 children of mixed socioeconomic background ranging in age from three to six years. Tasks were designed to assess gender constancy, knowledge of sex-stereotypes, differential memory and preference for sex-typed material, and gender categorization. Cognitive maturity was assessed with a conservation task and total recall on the memory task. Performance improved linearly with age on the gender concepts; individual children of both sexes learned the gender concepts in the same sequence; and cognitive maturity measures were positively related to performance on the gender concept tasks. Implications for self-socialization of sex-typing are seen in the development of gender concepts in young children. (Author)