The purpose of this study was to expand the literature on student persistence in community colleges through three research innovations. First, the literature on student persistence in community colleges was expanded by applying theory to the identification and testing of predictors. Second, it was expanded by validating retention prediction equations using independent data to test the generalizability of predictors. Third, it was expanded by determining the extent to which student major potentially mediates retention rates for community colleges. Aggregated student entry characteristic, external environment, and internal campus environment variables were obtained for 127 public community colleges in six states using the Integrated Postsecondary Education Data System (IPEDS). Data for six student majors were obtained from each state's community college governance structure. Descriptive statistics, multivariate linear regressions (stepwise), and ANOVA tests were used to address five primary research questions, with significance noted at p>0.05. The Braxton, Hirschy, and McClendon (2004) Theory of Student Departure at Commuter Colleges and Universities was used as the theoretical model for the study. The findings include: (a) a statistical model based on the Braxton et al. (2004) theory that can be developed to explain community college institutional retention, (b) the model equations validate with independent data, (c) the Braxton et al. (2004) model is ineffective for predicting retention by student major, and (d) retention rates differ by student major. The percentage of Black students enrolled, institutions located in small cities or suburban areas, and the number of part-time students enrolled emerged as generalizable predictors of institutional retention. [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.]