Women remain underrepresented in science, technology, engineering, and mathematics (STEM) at all levels of higher education, which has become a concern in the competitive global marketplace. Using both quantitative and qualitative analysis, this dissertation sought to learn more about how the campus climate and self-concept influence the degree aspirations of female undergraduate students majoring in STEM programs. Using the Beginning Post-Secondary dataset, regression analyses showed that a student's initial degree aspirations, SAT scores, and interactions with faculty were all positively related to their degree aspirations three years later. Interviews with seven current STEM undergraduates confirmed the importance of interaction with faculty and suggested undergraduate research and classroom experiences also play a role in the degree aspirations of STEM students. Three of the seven students interviewed began their undergraduate educations as non-STEM majors, suggesting that the traditional STEM pipeline may no longer be the norm. These findings suggest that both future research and current practitioners should focus on undergraduate STEM classroom and research experiences. Additionally, the characteristics of students who switch into STEM majors should be explored so that we may continue to expand the number of students pursuing STEM degrees. [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.]