Since the Texas Higher Education Coordinating Board launched their ambitious strategic plan entitled "60x30TX," higher education institutions must test and correctly place undergraduates in appropriate developmental or college-level courses based on undergraduates' academic ability. However, students who are required to take developmental education courses risk postponing their graduation as well as incurring additional expenses because federal financial aid is limited to 140 credits per student for an undergraduate degree. The purpose of this quasi-experimental, ex post facto quantitative study was to examine the effectiveness of two developmental mathematics models used in higher education institutions. Wambach, Brothen, and Dikel's proposed comprehensive developmental education theory that focused on the environment framed the study. Comparative research questions were posed about differences in course retention and completion among graduates at a Hispanic-serving institution. This study used a convenience sample of interest. Archival data was collected from existing student educational records were obtained. Yates X[superscript 2] was calculated to test hypotheses. The difference in the proportion of students who completed the corequisite developmental mathematics model was significant with a medium to strong effect size for both retention and completion in comparison to those who enrolled in the prerequisite developmental mathematics model. From results of the study, recommended is for students to be placed in a corequisite model. Recommended for future research is the replication of the study among a number of institutions and for a qualitative study that includes both faculty and laboratory staff to study experiences in prerequisite and corequisite models. [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.]