['Flexible sigmoidoscopy (FS) is a commonly used method for colorectal cancer screening. Women are more likely than men to have a FS with a limited depth of insertion, in part due to differences of anatomy and perception of pain.', 'The objective of this prospective single-blinded randomized clinical study is to assess satisfaction in women undergoing screening FS using an upper endoscope (E, diameter 9.8 mm) versus a standard sigmoidoscope (S, diameter 13.3 mm) as measured by pain and discomfort and overall satisfaction using a validated survey instrument. Secondary endpoints of FS efficacy included the depth of insertion of the instrument, frequency of polyp detection, and complication rate.', 'A total of 160 asymptomatic women undergoing screening FS were entered over a 4-month period (July through November 2002). All procedures were performed by two experienced physician assistants. The two groups were of similar age (E = 57.5, S = 58.2, p= 0.579) and had a similar rate of previous abdominal surgery (E = 51.2%, S = 45.0%, p= 0.428) or hysterectomy (E = 34.2%, S = 26.3%, p= 0.274). Depth of insertion of the scope was 54.5 cm (+/-9.2 cm) with the E and 51.6 cm (+/- 10.3 cm) with the S (p= 0.058). Polyps were found more frequently in the study group (18.3%) compared with the control group (p= 10.2%) though this did not reach statistical significance (p= 0.131). Overall satisfaction with FS was similar in both groups (p= 0.694) but pain and discomfort were less in the patients undergoing FS using the E (p= 0.006). Controlling for age and previous surgery the differences in pain scores remained significant (p= 0.035). Endoscopist assessment of procedure difficulty (p= 0.726) and complication rates (p= 0.614) was equivalent. Controlling for the presence of polyps, the total duration for the procedure was 7.2 min in the E group and 5.7 min in the S group (p= 0.008). There were no significant differences between women with and without hysterectomy on either overall satisfaction or pain and discomfort.'] Is screening flexible sigmoidoscopy using an upper endoscope better tolerated by women?