This quantitative study sought to examine the role of self-efficacy on the enrollment decisions made by women for a second year of high school physics. Not enough information is known about why there is a significant decrease in the proportion of women in second year high school physics programs after their introductory year. This study took place in a suburban Midwestern high school. After screening for outlier data, logistic regression was used to develop three predictive models on enrollment decision. This study showed that only level of self-efficacy due to mastery experiences is a statistically significant predictor of second year high school physics enrollment among both men and women. This result was due solely to the significance mastery experiences plays for women. Based on the results, teachers and scholars could focus more on the number and quality of mastery experience opportunities in the classroom for women in courses like physics and possibly other STEM courses. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]