Intubation of the ileum during colonoscopy, although well described, is not routinely performed. It can establish the completeness of colonoscopic examinations and is useful in the diagnosis of inflammatory bowel disease. However, the diagnostic utility of routine ileoscopy during all colonoscopic procedures has not been well studied. We prospectively evaluated ileal intubations in 138 patients undergoing colonoscopy. The incidence of a positive diagnosis from ileoscopy was 2.7% in asymptomatic patients undergoing surveillance colonoscopy, and 29% of patients complained of diarrhea (18% in non-HIV patients, 67% in HIV-positive patients). We feel ileal intubation is an important adjunct to colonoscopy, especially in patients with diarrhea.