Science, mathematics, and engineering (SME) disciplines lose potential female professionals as women move to other educational and career paths at higher rates than men. Also, the remaining women tend to cluster into particular fields. I frame these trends as identity-acquisition issues. Using identity theory, I examine links between gender, self-concepts, and perceptions of scientific others, focusing on how these contribute to students' SME interests and the resulting educational trajectories. The sample of 433 talented high school students was drawn from 10 SME summer programs conducted in 1995 and 1996. The students' interests fol- low common patterns by gender; identity theory helps to explain why. Key find- ings are as follows: (1) On average, girls' self-concepts are more like their percep- tions of same-sex others than those of boys, and more unlike their perceptions of other science students. (2) Discrepancies between self-concepts and perceptions of those in science-related disciplines are associated with lower interest in those disciplines. (3) Discrepancies explain some differences, by sex, in interest