This study examined the effects of gender identification and implicit and explicit gender stereotyping among undergraduate women enrolled in college-level calculus courses. Women's gender identification and gender stereotyping regarding math aptitude were assessed after the course's first midterm exam. Implicit, but not explicit, stereotyping interacted with gender identification to affect women's performance on their final exams and their desire to pursue math-related careers. Women who showed low gender identification and low implicit gender stereotyping performed best on the final exam, and women with high scores on both factors were the least inclined to pursue math-based careers. Implications for the under-representation of women in math and the hard sciences are discussed.