Endocavitary irradiation has been used for rectal adenocarcinoma and villous adenoma at St. Joseph's Hospital, Milwaukee, Wisconsin since 1978. The 52 patients treated since that time include 32 patients with adenocarcinoma, 19 patients with villous adenoma, and 1 patient with an adenomatous polyp and associated atypia. The average age of these patients (70.5 years) was a full decade older than the average age of all rectal cancer patients. The treatment was administered by a superficial contact machine with most patients receiving 80 Gy over four treatments in a period of 1.5 months. The overall local recurrence rate was 24% in the cancer group and 32% in the villous adenoma group. The 1-, 2-, and 3-year determinate disease-free survival rates were 90.4%, 78.6%, 74.2% and 80.4%; 60.3%, 45.2% for invasive adenocarcinoma and villous adenoma patients, respectively. There was no mortality and very little morbidity associated with the treatment. It is concluded that endocavitary irradiation is an effective alternative to surgery for the treatment of rectal cancer in selected cases. However, villous adenomas do not respond as well. Better results may be obtained for this group of patients by higher doses than were used in this study.