This study investigated the development of sex role orientation among adolescent girls, and explored its relationship with sports participation, self-esteem, and age at menarche. The instruments were administered to 134 girls yearly from Grades 6 to 10 (ages 11 to 15). The results obtained with the Bem Sex Role Inventory showed group mean increases in the masculine and feminine scale scores, and considerable shifting in sex role categorizations over the five years. However, individual differences were quite consistent during the five-year study, suggesting some degree of stability in sex role orientation during adolescence. Sports participants and girls with high self-esteem had greater masculine sex role orientations throughout adolescence, with no differences in feminine orientations. It was concluded that the relationship of sex role orientation with sports participation and self-esteem was not an interactive one, but was reflective of individual differences. These individual differences begin in late childhood, with the variables developing concurrently. Age at menarche did not affect sex role orientation.