OBJECTIVE Our purpose was to bring to the attention of gynecologists a subject not mentioned in a single textbook of gynecology, namely, genital fistulas resulting from diverticular disease of the sigmoid colon. METHODS We report our experience with 13 genital fistulas caused by sigmoid diverticulitis. RESULTS Ten fistulas involved the vagina, one the vagina and bladder, one the tube, and one the uterus. Average age of the patients was 68.6 years (range 54 to 89 years). Presenting symptom in 12 patients was a malodorous vaginal discharge. All with vaginal lesions had previously undergone total hysterectomy. A barium enema failed to demonstrate a fistula in 8 of 11 patients. Colonoscopy failed in 8 of 8 patients. All fistulas were demonstrated by retrograde dye studies. Ten patients operated on were cured. Three patients refused surgery; of these, 1 had intestinal obstruction, 1 may have had spontaneous closure of the fistula, and 1 is being observed. Surgery involved staged procedures in 2 patients, fistulectomy in 4, and bowel resection and anastomosis in 4. CONCLUSIONS Sigmoidovaginal fistulas are the most prevalent variety of cologenital fistula caused by sigmoid diverticulitis. The diagnosis should be considered in a patient > 50 years old who complains of a foul vaginal discharge and has a history of total hysterectomy. Its presence is best demonstrated by vaginogram. Surgical therapy is advised, the extent of which will rest on the surgeon's judgment of the severity of the inflammatory process found at exploration.