Management of stage A prostate cancer. Transrectal ultrasonography has defined a new category of stage A disease, namely nonpalpable lesions diagnosed by needle biopsy. How this type relates to classic stage A disease is unclear. Stage A1 carcinoma becomes clinically significant only in a distinct minority of patients, and even in this group, progression does not necessarily mean significant morbidity or death from prostate cancer. An aggressive approach is not justified. In contrast, stage A2 cancer is usually virulent, and aggressive therapy with curative intent is justified in patients of appropriate age and health. Both radical prostatectomy and external irradiation appear to provide long-term survival rates superior to those obtained with observation alone, but nearly 20% of these patients will die of cancer despite therapy. Unfortunately, forecasting the outcome in an individual case is still not possible, and efforts to identify prognostic features must continue. In the meantime, emotional arguments in favor of the treatment of all discovered cancers must be suppressed by an informed and objective understanding of the natural history of nonpalpable prostate cancer and the potential impact of treatment. 