Drawing upon self-efficacy theory (Bandura, 1997), the purpose of this study was to examine academic self-discipline (ASD) as a mediator of the relationship between academic self-efficacy (ASE) and college GPA, as well as the feedback effect of previous academic performance on subsequent ASE and ASD. To test this research question, I used cross-sectional and longitudinal data with three time points from 560 first-year and second-year college students. The cross-sectional analysis confirmed ASD was a mediator of the ASE-GPA link. By contrast, the longitudinal analysis did not support the ASE ? ASD ? GPA associations, although a GPA feedback effect on ASE and ASD was found at time 2. The study findings suggest ASD may be a more practical and functional predictor than ASE of academic performance. [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.]