Women take qualifying exams and enter medical school at substantially lower levels than predicted by their interest in medical degrees at the end of high school. We examined how science course experiences contribute to gendered attrition in premed using a multicohort data set of 8,253 undergraduates taking the traditional premed sequence of introductory science courses at a public research university between 2008 and 2016. Gendered attrition was not based in academic performance, was specific to high-performing women, and yet was grounded in competency beliefs. The result is that high-performing women often graduate with lower paying, lower status degrees. Motivational interventions in premed science courses will be critical for retaining high-performing women in premed, an important outcome with implications for equity and women's health.