Background: Prediction of a technically difficult colonoscopy may influence patient selection and procedure scheduling. Identification of predictive factors may be difficult because a common endpoint used to evaluate the success of colonoscopy is intubation of the cecum, which is usually achieved. The goal of this study was to examine the feasibility of using an alternative measure, time required for cecal intubation, to identify factors that can impact performance of colonoscopy. Methods: The time required for cecal intubation was prospectively recorded for 802 consecutive outpatient colonoscopies performed by 7 experienced gastroenterologists. Patient data collected included height, weight, age, bowel habits, surgical history, and findings at colonoscopy. Forty-seven examinations that were stopped because of disease or unacceptable bowel preparation were excluded. The impact of the patient characteristics of the remaining sample of 755 patients on the median time required for cecal intubation for men and women was examined. Results: Older age and female gender, body mass index ≤25.0 (regardless of gender), diverticular disease in women, and a history of constipation or reported laxative use in men were predictors of difficult colonoscopy. Conclusions: By using median time required for cecal intubation, several patient characteristics were identified that may predict technical difficulty at colonoscopy. These findings have implications for practice and teaching. (Gastrointest Endosc 2001;54:558-62.)