This research study focused on the relationship between student outcomes (indicated by Advanced Placement enrollment, Advanced Placement course grades, Advanced Placement exam scores, Advanced Placement exam passing rate) and student demographic factors as well as student support programs (such as AVID, an AP Incentive Program, and a summer AP preparation program known as Summer Bridge) among the underrepresented students, specifically Hispanic and African American students, in an urban district in Southern California. The target sample included 4 grade-level cohorts of students from 6 comprehensive high schools within the district totaling 22,227. This correlational study utilized logistic and multiple regressions to analyze the data; and the results were consistent with research literature, indicating an overall significant strong relationship among student demographic factors of gender, socioeconomic status, ethnicity, and parent education level and AP enrollment and achievement. It was predicted and found that females enrolled in more AP courses and achieved better course grades than males; but males in the youngest cohort earned higher AP exam scores and passing rates than females. Hispanics, African American, and Asian students had lower course grades, AP exam scores, and AP exam passing rates than Whites even though Asians enrolled in AP courses 1.6 times more than all other subgroups. The vast majority of AP students had parents who earned less than a college degree and had lower AP enrollment and achievement. When controlling for student demographic factors, more AVID students were likely to enroll in AP courses than non-AVID students in 2 of the 4 cohorts. Nevertheless, AP AVID students earned lower AP course grades, lower AP exam scores, and lower AP exam passing rates than non-AVID students. However, the Summer Bridge participation positively predicted increased AP enrollment and achievement. While this study did not control for base academic achievement such as overall grade point average or standardized test data, future studies could utilize longitudinal tracking of the academic progress of AP students from kindergarten through the twelfth grade which could provide policy-makers evaluations on effective teaching practices, interventions, and student support programs that increase eventual AP enrollment and achievement. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]