Subtotal colectomy with ileorectostomy has been proposed for the management of colon inertia-type constipation. However, many patients experience frequent bowel movements, watery diarrhea, or both after such a treatment. The purpose of this study is to determine the proper colectomy with which to treat colon dysmotility constipation without the negative side effects of frequent bowel movements, watery diarrhea, or both. Forty idiopathic constipation patients were studied. All of the patients showed a prolonged right or left colon transit time and normal transit time of the sigmoid and rectum. They received different types of colectomies (left, right, and subtotal) according to the distribution or accumulation of markers in the colon. Within 3 months of surgery, all of the patients experienced a dramatic improvement of their symptoms without frequent bowel movements or watery diarrhea. No significant complications developed after surgery. All the patients were followed up for at least 2 years. Most of them (37 cases) still had satisfactory bowel movements and no other constipation symptoms. However, 3 of the 40 cases developed symptoms of constipation 1 1/2 to 2 years after surgery. They all received subtotal colectomy with ileorectal anastomosis subsequently. They reobtained satisfactory bowel movements and experienced a subsidence of other constipation symptoms 3 months later. These results suggest that directed segmental colectomy can improve colonic inertia constipation without the consequence of frequent bowel movements and diarrhea.