In a retrospective review, 62 patients treated for rectal cancer by contact (endocavitary) irradiation at The Cleveland Clinic Foundation were analyzed. This treatment modality delivers high dose, low penetration irradiation to a rectal cancer by direct contact of a 50 KV x-ray source through a special proctoscope. Cancers selected for this treatment include small (3 cm or less), mobile tumors without presacral lymphadenopathy that are within reach of digital examination and are well- or moderately well-differentiated adenocarcinomas. Between 1973 and 1984, 62 patients (37 males, 25 females) were treated--46 by contact irradiation alone and 16 by contact irradiation after excisional biopsy. The median tumor dose was 12,000 rads administered in four fractions at monthly intervals. Mean follow-up was 31 months. Fifty-six patients (90 percent) were disease-free at the time of review or death (ten died from unrelated causes). Eleven patients (18 percent) developed local recurrence but eight of these without distant metastases were rendered disease-free by other treatment--six by surgical resection and two by further radiotherapy. Mean time since secondary treatment is 20 months. Three patients are alive with incurable disease and three have died from cancer--in three of these six patients there was no evidence of local disease. Ulcerated tumors developed local recurrence in five of 17 cases (29 percent) while polypoid tumors recurred locally in six cases (14 percent). Morbidity from the treatment was minor in nature. It is suggested that contact (endocavitary) irradiation is effective treatment for carefully selected cases of rectal cancer.