The standard surgical therapy for severe idiopathic constipation is total colectomy with ileorectal anastomosis, but this results in intractable diarrhoea in a third of the patients and recurrent constipation in another 10%. Studies which employ either radio-isotopes or radio-opaque markers permit the delineation of regional delay in colonic transit. Based on these studies, and evidence that the rectum is also abnormal in these patients, we have performed a left hemicolectomy with rectal excision in 2 patients with proven left colonic delay. After 2 and 3 years of follow-up, both patients have normal frequency, transit studies and anorectal physiology studies. Segmental resection based on physiological studies may offer better relief of symptoms with a lower chance of side effects in selected patients.