BACKGROUND: The occurrences of dental caries among San Diego Regional Center (SDRC) adult clients are unknown. SPECIFIC AIM: To estimate the prevalence and correlates of dental caries in a sample of adults with intellectual or developmental disabilities (IDDs) residing in southern San Diego, California. METHODS: Dental screening exams and brief interviews with adults with IDDs or their knowledgeable primary caregiver were conducted between September 2013 and April 2014. The large (n=422), diverse, convenience sample included both facility and community-dwelling adults served by the SDRC. The trained dental team from San Ysidro Health Center's Specialty Dental Care clinic screened adults visually to assess dental caries. Medical record data were collected by SDRC prior to the screening. Informed consent was obtained from the participants or from his/her informed surrogate with legal authority. Descriptive, bivariate chi-square analyses and binary logistic regression were conducted with presence of caries as the final outcome. RESULTS: The prevalence of untreated caries in this sample was 37.3% overall (30.0% in facilities, 49.6% in community). The mean (standard deviation) numbers of decayed teeth; missing teeth; and decayed, missing and filled (DMF) teeth were 0.9(1.9), 2.7(4.1) and 6.4(4.9) respectively. Having cerebral palsy, epilepsy, or other disabilities similar to IDDs, and flossing daily were each negatively associated with dental caries in the bivariate analyses. Positive bivariate associations with caries were observed for high levels of plaque, calculus, dental visits over 1 year ago, pain, needing treatment, and not being able to find a willing dentist. The final logistics regression model presented with significant results for cerebral palsy, dental visits over 1 year ago and daily flossing. DISCUSSION: Dental caries prevalence was higher among adults with IDDs. They have significant barriers to oral health care and poor oral hygiene that is associated with occurrence of dental caries. This study will aid in planning for future dental care and identifying potential caries risk factors.