OBJECTIVES: I. Determine the maximum tolerated dose of 3-dimensional conformal radiotherapy to the prostate gland and immediately surrounding tissues in patients with stage II or III adenocarcinoma of the prostate. II. Determine the normal tissue toxicity rate of this regimen in the rectums and bladders of these patients. III. Determine local control by clinical and pathologic examination and by PSA determinations in patients treated with this regimen. IV. Determine the distant failure and overall survival of patients treated with this regimen.