Colonoscopy sometimes causes pain during insertion,especially in difficult cases.Over-insufflation of air causes elongation or acute angulations of the colon,making passage of the scope difficult and causing pain.We previously reported a sedative-risk-free colonoscopy insertion technique,namely,“Water Navigation Colonoscopy”.Complete air suction after water infusion not only improves the vision,but also makes water flow down to the descending colon,while the sigmoid colon collapses and shortens.While non-sedative colonoscopy can be carried out without pain in most cases,some patients do complain of pain.Most of these patients have abnormal colon morphology,and the pain is caused while negotiating the “hairpin” bends of the colon.The “hairpin” bends of the colon should be negotiated by gently pushing the full-angled colonoscope.The proximal 10-20 cm from the angulated part of the conventional colonoscope is stiff,with a wide turning radius,therefore,a conventional colonoscope cannot be negotiated through the “hairpin” bends of the colon without stretching them and causing pain.The “passive-bending colonoscope” has a flexible tip with a narrow turning radius,so that the scope can be negotiated through the “hairpin” bends of the colon with a minimum turning radius and minimal discomfort.Therefore,the intubation and pain-reducing performance of the “passive-bending colonoscope” was assessed in difficult cases. Colonoscopy sometimes causes pain during insertion, especially in difficult cases. Over-insufflation of air causes elongation or acute angulations of the colon, making passage of the scope difficult and causing pain. We previously reported a sedative-risk-free colonoscopy insertion technique , “Water Navigation Colonoscopy ”. Complete air suction after water infusion not only improves the vision, but also makes water flow down to the descending colon, while the sigmoid colon collapses and shortens. Whilst non-sedative colonoscopy can be carried out without pain in most cases, some patients do complain of pain. Mother of these patients have abnormal colon morphology, and the pain is caused while negotiating the “hairpin ” bends of the colon. “hairpin ” bends of the colon should be negotiated by gently pushing the full-angled colonoscope.The proximal 10-20 cm from the angulated part of the conventional colonoscope is stiff, with a wide turning radius, therefore, a conventional colonoscope cann ot be negotiated through the “hairpin ” bends of the colon without stretching them and causing pain.The “passive-bending colonoscope ” has a flexible tip with a narrow turning radius, so that the scope can be negotiated through the “Hairpin” bends of the colon with a minimum turning radius and minimal discomfort.Therefore, the intubation and pain-reducing performance of the “passive-bending colonoscope” was assessed in difficult cases.