This study sought to determine whether clinical psychology doctoral students hold uniquely stigmatizing views of adults with substance use disorders (SUDs) compared to adults with other clinical disorders. Through the use of clinical vignettes and attitudinal measures, three hypotheses investigated clinical psychology doctoral students' attitudes towards adult clients with SUDs, perceived attributional causes of SUDs, and future interest in working with SUD clients. One hundred and fifty-six clinical psychology doctoral students participated in this study, with the majority of participants attending graduate programs in the San Francisco Bay Area. To date, this is the largest known study of clinical psychology doctoral students' attitudes towards SUD clients. The results of this study yielded several significant findings. Overall, participants endorsed more negative attitudes towards SUD clients when compared to a client with major depressive disorder (MDD). Additionally, respondents attributed SUDs to poor willpower with greater frequency than they attributed MDD to poor willpower. Finally, participants who expressed negative reactions towards an SUD client, also demonstrated an overall lack of interest in working with SUD clients in the future. This study also found several significant relationships with regard to participant demographic variables and attitudes. First, female-identified participants reported more negative reactions across all mental health conditions compared to male or transgender-identified participants. Second, first-year doctoral students endorsed the least negative attitudes towards both SUDs and MDD as compared to more advanced doctoral students. Third, LGBTQ-identified participants and participants with personal or known experience with substance abuse, expressed the greatest interest in working with SUD clients. Fourth, participants with a postmodern theoretical orientation, namely narrative, multicultural, and systems, expressed more interest in working with SUD clients than participants who identified as psychodynamic or behaviorally-oriented. The findings of this study have numerous implications for clinical psychology graduate programs with regard to clinical training and curricula development and highlight a need for future research in the areas of substance use disorders, mental health stigma, and graduate training in clinical psychology. [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.]