The purpose of this study was to determine the antecedent conditions that contribute to post-secondary education (PSE) completion for students with disabilities, taking into account institutional experiences associated with social integration. A prospective longitudinal design was used to analyze data from the National Longitudinal Transition Study-2. The study sample consisted of youth who were currently enrolled in vocational schools, two-year community colleges, and four-year universities six years after high school exit. Logistic regression was used to examine the relationships between pre-entry variables and PSE completion. To test the hypothesis of mediation, the causal step approach (Baron & Kenny, 1986) was used. Findings indicated that self-advocacy, participation in work-study or paid employment, participation in extra-curricular activities, and development of vocational skills as a primary transition goal significantly predicted PSE completion. Students who participated in work-study or paid employment reported higher levels of PSE completion. Students who provided input in IEP meetings were less likely to report completing PSE compared to peers who took leadership roles in IEP meetings. Both participating in extra-curricular activities and developing vocational skills as a primary transition goal were negatively associated with PSE completion. The mediation analysis revealed that it is unlikely that institutional experiences examined in this study mediate the relationships between pre-entry variables and PSE completion. Findings further showed that many of the factors considered in the student integration model (Tinto, 1975, 1987, 1993) are positively related to PSE completion for students with disabilities. [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.]