President Obama has recently raised awareness on the need for our nation to grow a larger pool of students with knowledge in science mathematics, engineering, and technology (STEM). Currently, while the number of women pursuing college degrees continues to rise, there remains an under-representation of women in STEM majors across the country. Although research studies offer several contributing factors that point to a higher attrition rate of women in STEM than their male counterparts, no study has investigated the role that high school advanced placement (AP) math and science courses play in preparing students for the challenges of college STEM courses. The purpose of this study was to discover which AP math and science courses and/or influential factors could encourage more students, particularly females, to consider pursuing STEM fields in college. Further, this study examined which, if any, AP math or science courses positively contribute to a student's overall preparation for college STEM courses. This retrospective study combined quantitative and qualitative research methods. The survey sample consisted of 881 UCLA female and male students pursuing STEM majors. Qualitative data was gathered from four single-gender student focus groups, two female groups (15 females) and two male groups (16 males). This study examined which AP math and science courses students took in high school, who or what influenced them to take those courses, and which particular courses influenced student's choice of STEM major and/or best prepared her/him for the challenges of STEM courses. Findings reveal that while AP math and science course-taking patterns are similar of female and male STEM students, a significant gender-gap remains in five of the eleven AP courses. Students report four main influences on their choice of AP courses; self, desire for math/science major, higher grade point average or class rank, and college admissions. Further, three AP math and science courses were highlighted throughout the study. First, AP Chemistry was described as a foundational course necessary for the challenges of STEM courses. AP Calculus was considered a course with practical benefits across STEM majors. Finally, AP Biology was found to be a gateway course, which inspired students to continue to pursue STEM majors in college. All three courses were strongly recommended to high school students considering a STEM major. The findings will help grow a larger and equally prepared pool of females and males and help sustain a more even distribution of women across STEM fields. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]