One-thousand three hundred fifty-one consecutive colonoscopies were performed in an office setting without fluoroscopy. Three different models of colonoscopies were utilized; all were manufactured by the Olympus Corporation of America, and included a videoendoscope, a CF-20L immersible OES-type instrument, and an older fiberoptic colonoscope, CFLB-3W. In all colonoscopies, the cecum was reached in 95.9%, even when an obstructing lesion or stenosis was present. Total intubation was performed in 97% of cases with the videoendoscope, 95.5% with the CF-20L, and 95.7% with the CFLB-3W. In a subgroup of 865 colonoscopies, total colonoscopy was performed in 98% of cases when obstructing lesions (carcinoma or stricture) were excluded from analysis. In this subgroup, total colonoscopy could not be performed in 16 patients because of colonic fixation, tortuosity, or for unknown anatomical reasons. Forty-five percent of this subgroup was female, but of the 16 patients in whom total colonoscopy was not possible, 15 were women, 5 of whom had a previous hysterectomy. We conclude that in the absence of any obstructing lesion, an expert can perform complete colonoscopy in 98% of examinations, and in 95% of all patients presenting for colonoscopy. Total colonoscopy may be more difficult in women than men, but a previous hysterectomy does not seem to adversely affect the ability to perform colonoscopy. The type of instrument used for colonoscopy does not impact on the ability to visualize the entire colon.