Adults with intellectual and developmental disabilities (IDD) frequently have comorbidities that might interfere with colonoscopy preparation and examination. In this article, the authors review their experience with colonoscopies performed from 2002 through 2010 on adults with IDD at a state institution to evaluate quality and safety of examinations and to formulate a plan to improve quality. In addition to IDD, these individuals had associated comorbidities, including digestive motility disorders and epilepsy. Results were compared with examinations performed in a random group of 40 adults without IDD examined between 2004 and 2008. The authors discovered a high rate of colonoscopy preparation failure and failed examinations in the IDD group. Preparation complications were also noted. The authors recommend careful preoperative evaluation of individuals with IDD and limiting colonoscopy to individuals who are able to tolerate preparation and comply with hydration.