A study of 57 cancer patients with colo-urinarytract fistulas has been presented to define incidence, etiology, anatomy, clinical manifestations, pathology, and management of this difficult problem. Conclusions reached include: 1) Fistulas occur most commonly after surgical treatment and irradiation, and are frequently associated with recurrent cancer. 2) In patients in whom the fistulas are present at the time of manifestation of their cancers (usually colonic cancer) all attempts should be made to achieve a curative resection. 3) Patients in whom fistulas develop after treatment of their cancer must be evaluated with regard to the presence of recurrent disease. 4) Attempts at local treatment of irradiation-induced fistulas have not met with success, and the treatment of choice is usually diversion of fecal and urinary streams. 5) Patients who have fistulas in association with unresectable recurrent disease are best managed by palliative bypass of the fistulas. 6) For those patients who have fistulas in association with resectable recurrent disease, the procedure of choice is resection, usually by pelvic exenteration. 7) These patients need a team approach for successful management of their problems. The team should include a social worker, who can help the family cope with the patient's illness.