Analyzing 60,000 undergraduate applications to the University of California, the authors find that extant gender segregation of academic disciplines also manifests in intended major choice. Gender and SAT Math scores together strongly predict intent to major in biology and engineering, the most popular and gender-segregated majors. Using natural language processing, the authors also find that author gender is more predictive of essay topics written by prospective engineers than prospective biologists. Women intending to major in engineering write about essay topics that signal their gender identity to a greater degree than women intending to major in biology, perhaps to mitigate gender-transgressive academic commitments.