In the US, women go to college at higher rates than men, but they are less likely to choose applied-STEM college majors or occupations. Using the National Longitudinal Survey of Youth 79 and 97 datasets, Todd and I assess the importance of adolescent skill profiles and high school coursetaking in explaining gender disparities in four-year college completion, college major, and occupational choices. We consider five cognitive skill measures (math, verbal, science, administrative, and mechanical) and one non-cognitive measure and examine gender skill convergence over a twenty-year time span. Results show that highschool-aged women in the NLSY97 cohort reached parity with men, on average, in mathematics skills and exceeded men in verbal and noncognitive skills, but they lag behind in mechanical and, to a lesser extent, science skills. To identify the skill sets, coursetaking, and family background characteristics that best predict entry into STEM majors and occupations, we estimate logistic and nonparametric Random Forest models. The estimates reveal that a combination of mathematics and mechanical skills, along with intensive high school exposure to science and math courses, are key predictors of choosing STEM majors and careers. A nonparametric decomposition approach is developed and used to quantify how eliminating gender skill disparities would affect entry into STEM fields. To further understand where the leaks are in the STEM career pipeline, I develop and estimate a dynamic model that describes decision-making from high school to early career to examine four sources of female under-representation in STEM: initial skill gaps, preference differences, wage disparities in STEM sectors, and aversion to male-dominated occupations. In the NLSY79 dataset, males show a higher interest in STEM coursework and better STEM skills by 10th grade, primarily in mechanical skills, and skill disparities wider in high school. Simulation results show that mechanical skills are more important than math skills in explaining women's low participation in applied-STEM fields and have countervailing effects on college enrollment and the selection of applied-STEM majors and occupations. Closing gender skill gaps upon exiting high school reduces female under-representation by 67% in applied-stem majors and 31% in applied-STEM occupations. Removing the preference for female-dominated workplaces reduces female under-representation by 29% in applied-STEM majors and 85% in applied-STEM occupations. Equalizing wage offers in STEM sectors has a smaller effect (3% in majors and 10% in occupations). Mandating more highschool STEM courses increases overall STEM participation for both males and femalesbut does not address the gender gap.