Sexist and racist STEM stereotypes persist in youth and contribute to gender and ethnic gaps in careers in science, technology, engineering, and mathematics (STEM). For female and some ethnic minority students, the internalization and psychological threat of negative stereotypes can present a barrier to full STEM participation by interfering with achievement and reducing self-efficacy and interest in STEM. Nonetheless, self-affirming values and strong social identities are emergent resources that these individuals can use to transcend such barriers. Research presented in this symposium will address the development and change of STEM attitudes and achievement in adolescents and young adults of diverse ethnic and socioeconomic backgrounds, taking into account the intersection of gender and ethnic identities as they develop. Presenters will discuss basic and applied psychological research addressing how developing social identities related to gender and ethnicity contribute to STEM attitudes and achievement and how implicit biases influence the retention of qualified and interested STEM students. They will report new research demonstrating the long-term efficacy of interventions designed to enhance positive identity and mitigate the deleterious effects of gender and ethnic stereotypes on achievement.