The data concerning the influence of gender and age on a patient's toleration of and the technical difficulty of colonoscopy are conflicting. One hundred eighty patients (108 women and 72 men) undergoing colonoscopy were categorized into three age groups: the young (aged 2040 years), the middle-aged (aged 41-60 years), and the old (aged 61-75 years). The endoscopists assessed the examination immediately after the procedure. The patients completed a questionnaire before leaving the endoscopy unit and again 2 weeks later. The women rated colonoscopy after the procedure more painful (p < 0.01) and in the repeat questionnaire more painful (p < 0.05) and more difficult (p < 0.05) than men. Also, the endoscopists judged colonoscopy to be more difficult (p < 0.001) and the time taken to reach cecum longer (p < 0.01) for women. The young experienced more discomfort than the middle-aged or the old, as evaluated after the procedure (p < 0.05). In the repeat questionnaire, the young reported more discomfort and pain than the middle-aged (p < 0.05). The endoscopists also judged the examination to be more difficult and the time taken to intubate cecum longer for the old than for the middle-aged (p < 0.05) or the young (p < 0.01). Correspondingly, the examination time was shorter among the young when compared with the middle-aged (p < 0.05) or the old (p < 0.001). The young were least willing to repeat the examination (p < 0.05). Colonoscopy is less tolerable and more difficult for women. Although colonoscopy among the old patients was technically more difficult, they tolerated the procedure better than the young.