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We previously reported that the sigmoid-descending colon junction becomes linear and the colonoscope can be readily inserted into the descending colon in the left semiprone position. In addition, we encountered a situation whereby the sigmoid colon becomes more linear and the colonoscope can be more straightly inserted in the sigmoid colon when the colonoscope is inserted with twisting to the left in the left semiprone position. Therefore, our new insertion method was devised so that the colonoscope neutral position was rotated 45 degrees to the left compared to our conventional insertion method, and this method was performed to determine whether the colonoscope looping rate in the sigmoid colon can be reduced. The colonoscope looping rate in the sigmoid colon could be reduced by using our new insertion method. These results suggest that safer colonoscope insertion is possible by using our new insertion method compared with our conventional insertion method.