Background: A significant number of students enrolled in postsecondary institutions have a disability. Like many young adults, college students with disabilities have an elevated risk of substance use. However, research on substance use in this population is limited. Objectives: This dissertation aims to: 1) Examine the prevalence of disability in U.S. college students by student characteristics, including disability status; 2) Present associations between disability status, sociodemographic characteristics, and substance use among college students; and 3) Explore the individual, interpersonal, institutional, and public policy factors affecting service utilization by college students with disabilities. Methods: A mixed methods design was employed in this study. Data from the 2015 National Survey on Drug Use and Health (NSDUH) public use data file was analyzed. Purposeful sampling was employed for in-depth interviews with key informants at Rutgers University who provide services to students with disabilities. Results: An estimated 2.6 million (12.6%) college students had a disability. The most common type of disability was cognitive impairment (7.3%). College students with any disability had higher odds of current tobacco use (AOR = 1.31; 95% CI 1.01-1.69) and reported more ever use, past year use, and current use of illicit drugs (p<0.001) than their nondisabled peers. Personal barriers emerged as dominant themes for service utilization by students with disabilities.Conclusions: This dissertation documents the high prevalence of substance use among college students with disabilities. It also highlights the many barriers to service utilization for this population. Understanding the risk factors for substance use and strategies for prevention and treatment are important to people with disabilities, disability service providers, and public health policymakers. Hence, there is a need for the development of health improvement plans for college students that integrate inclusive policy, systems, and environmental strategies. [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.]