One of the earliest indications that a student may be interested in STEM paths is the students' own self-efficacy for science as well as how they may see themselves in a STEM career as part of their science self-identity (Schlegel et al., 2019). Currently, there is a need to contribute to research that can assist agencies such as the National Science Foundation (NSF), Department of Education and the National Academy of Sciences in advising the nation, including high schools and postsecondary institutions on ways to increase the enrollment of students in STEM-related careers. This study examined the extent to which science self-efficacy and science identity are related to postsecondary STEM degree selection, with special attention to how factors like race, gender, SES status and urbanicity influence science self-efficacy and science identity and how they may be predicative of postsecondary STEM degree selection. Correlation analysis was conducted to quantify the relationship between science identity and STEM degree selection, as well as between science self-efficacy and STEM degree selection. Correlation analysis by subgroup was conducted to examine differences in science identity and science self-efficacy between students based on the demographic characteristics. And binary logistic regression was conducted using the inputs of science identity, science self-efficacy, and demographic characteristics as variants to estimate STEM degree selection. Results of this study suggests that science identity and science self-efficacy are positively correlated with a student selecting a STEM degree. Relationships between science identity and self-efficacy with STEM degree selection among the demographic characteristics was also positively correlated. Black/African Americans and students from the lowest SES both are less likely to select a degree in STEM, while all other demographics show a positive predictive pattern. This work can be used to guide science education policy at the local, state, and national levels, and to direct science education programming in formal and informal settings including those at the high school level in ways to better prepare and encourage students into STEM careers. [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.]