Concepts regarding the surgical treatment of cancer of the prostate have changed significantly at the Mayo Clinic. Rather than emphasizing radical prostatectomy only for low-grade (grade less than or equal to 2) and low-stage (less than or equal to T1/B1) lesions--which may be equally well treated at less than ten years, in regard to crude survival, by radiotherapy--we believe that radical prostatectomy is particularly suitable for lesions of higher local stages, including those with regional node extension. This view is based on a large experience (less than 2,000 cases) with the radical surgical treatment of cancer of the prostate and on the realization that conservative single-modality treatment (hormonal or radiotherapy) for advanced local Stages (C and D1) provides poor cause-specific survival and nonprogression rates and may lead to high local morbidity. The treatment of Stage D1 prostate cancer was thought to be not amenable to surgical treatment, and many have recommended observation only. In 266 patients (mean age, 64 years) followed one to twenty-one years (mean, 4.7 years), immediate adjuvant orchiectomy at the time of radical prostatectomy performed in 162 patients (61%) resulted in a highly significant (P less than 0.0001) decrease in progression compared with no immediate orchiectomy in 104 patients (39%). The ten-year overall and local nonprogression rates for those undergoing immediate orchiectomy were 80 percent and 98 percent, respectively; median time to progression for the no-immediate-orchiectomy group was less than 4.5 years, and the local recurrence rate was 25 percent at ten years. Of all the pathologic variables, only DNA ploidy pattern had a significant influence on progression and cause-specific survival. Also, in patients with D1 disease and a nuclear DNA diploid pattern, immediate adjuvant orchiectomy resulted in a nonprogression rate of 100 percent at ten years compared with virtually 0 percent in those with a nondiploid tumor and no immediate orchiectomy. Because 42 percent of the patients with D1 disease in the Mayo Clinic experience have DNA diploid tumors, adjuvant orchiectomy in this group results in no progression or prostate cancer death. Patients with Stage D1 prostate cancer and DNA nondiploid pattern undergoing prostatectomy should be entered in prospective adjuvant innovative treatment protocols since these tumors do not seem to respond to early hormonal manipulation.