In the series presented here, survival patterns at 15 years after radiotherapy for patients with clinical stage A carcinoma of the prostate did not deviate significantly from those of an age-matched peer group. For patients with clinical stage B disease (nodular disease that did not exceed involvement of one lateral lobe), survival was only 5% less at 15 years than for the age-matched group of California men. This was in spite of the fact that the lymph node status and the true incidence of capsular penetration were unknown. Moreover, the patients were not stratified by histopathologic grade or by either acid phosphatase or prostate-specific antigen values. If one were to restrict the patients to those with intermediate and low Gleason scores, normal acid phosphatase, and low prostate-specific antigen values, it is likely that there would have been no difference between the survival of those with prostatic cancer and their age-matched peers. As one deviates from these conservative selection criteria and includes patients with more advanced stages, the likelihood of achieving 15-year survival diminishes. With radiation treatment, however, patients whose disease, by clinical examination, extends beyond the prostate and who seem too advanced for radical prostatectomy still may have a 20 per cent to 30 per cent chance of 15-year survival.