A randomised prospective trial compared safety and patient tolerance for one-man method with two-man method undergoing colonoscopy. Eighty patients were randomized to 1 of 2 groups: the two-man method group (n = 40); or the one-man method group (n = 40). All colonoscopic examinations were performed by the same endoscopist to reduce skill-based variation. Patient tolerance for colonoscopy was evaluated with a numerical rating scale ranging from 0 for painless to 5 for maximal pain. Cardiopulmonary parameters were recorded during the procedure. Patients receiving one-man method had lower pain score than two-man method. The length of the scope reach to the cecum was shorter in the one-man group than the two-man group. The patients underwent two-man colonoscopy had higher maximum increase in heart rate during the procedure compared with one-man group. One-man colonoscopy can improve patient tolerance and reduces patient pain by decreasing the redundancy of colonoscope during the procedure.