This study seeks to advance and expand research on college student success. Using multinomial logistic regression analysis, the study investigates the contribution of psychosocial variables above and beyond traditional achievement and demographic measures to predicting first-semester college grade point average (GPA). It also investigates if achievement, demographic, and psychosocial variables differentially predict college GPA for groups of students with distinct levels of past academic achievement. Further, it relies upon a social-cognitive theoretical framework to explain the relationship among achievement, demographic, and psychosocial variables and to contextualize results. Results underscore the importance of known achievement, demographic, and psychosocial predictors of college GPA, provide refined information about those predictors, and offer new insight and evidence regarding psychosocial variables in particular. Importantly, findings regarding achievement motivation/academic engagement and the personality trait of extroversion/introversion highlight achievement motivation's relevance to the success to all students and personality's relevance to a specific subset of high achieving students. Moreover, a new instrument (i.e., Student Strengths Inventory) is studied in this research, and results thereby add to the literature in regard to this concise instrument. The application of findings to higher education practices and policies may help to better identify and prepare students for success and may contribute to individual students' abilities to obtain their goals of earning college degrees as well as to national goals aimed at increasing the number of college-educated citizens in the United States. [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.]