We reviewed 60 cases of incidental carcinoma of the prostate treated conservatively. Subclassification of incidental carcinoma was based on histologic grade and tumor size. Stage A1 was defined as a low grade (grade I) and focal lesion, and stage A2 as a high grade (grade II, III) or diffuse lesion. The distinction between focal and diffuse was set at three chips in a transurethrally resected specimen or a diameter of 5 mm for a total lesion in an enucleated specimen. Patients with stage A1 tumors did significantly better (p less than 0.05) than those with A2, the 5-year survival rates being 88% and 70%, respectively. It is believed that patients with stage A2 should be treated aggressively. However, conservative therapy is recommended for the patients with stage A1 prostate cancer.