PURPOSE To evaluate the role of endocavitary irradiation and wide local excision followed by irradiation in the treatment of early-stage rectal adenocarcinoma. MATERIALS AND METHODS Sixty-five patients with early-stage adenocarcinoma of the rectum were treated with endocavitary irradiation (n = 20) or wide local excision followed by external-beam irradiation (n = 45) between 1974 and 1994 at the University of Florida. All patients were monitored for a minimum of 2 years or until death. RESULTS The rates of local-regional control at 5 years were 80% after endocavitary irradiation and 86% after wide local excision and radiotherapy. The ultimate 5-year local-regional control rates were 85% and 92%, respectively. Multivariate analysis of local-regional control with sphincter preservation showed that tumor configuration (exophytic v ulcerative) significantly influenced this end point; local-regional control was decreased in patients with ulcerated cancers. Five-year cause-specific survival rates were 84% after endocavitary irradiation and 88% after wide local excision and radiotherapy. Multivariate analysis revealed that tumor configuration significantly influenced cause-specific survival; patients with ulcerated tumors had a worse prognosis. CONCLUSION Endocavitary irradiation is a highly effective treatment for properly selected patients with early-stage rectal adenocarcinoma. Patients with less favorable lesions that appear to be limited to the muscularis propria have a high chance of cure with sphincter preservation after wide local excision and external-beam irradiation.