One hundred and sixty-seven patients with newly diagnosed, previously untreated prostatic adenocarcinoma, during the period between July, 1971 and March, 1934, were studied. The histopathologic specimens of the prostate were classified by the Japanese General Rules of Prostatic Cancer (JGRPC) and by Gleason's classification. The number of patients with well, moderately and poorly differentiated prostatic carcinomas according to the JGRPC classification was 42, 74 and 51 respectively, and the number of the patients with Gleason's pattern 1, 2, 3, 4, and 5 was 24, 20, 32, 43 and 48, respectively. The number of patients with Gleason's score (primary plus secondary pattern) 2 to 4, 5 to 7 and 8 to 10 groups was 40, 76 and 51 respectively. There was no significant difference in survival rate between well and moderately differentiated groups, but the survival rate of the group with poorly differentiated tumor was significantly lower than that of the moderately differentiated (p less than 0.01) and well differentiated (p less than 0.001) groups. There was no significant difference in 10-year survival rate between the score 2-4 and score 5-8 groups, but the score 9-10 group had a significantly lower survival rate than the score 5-8 group (p less than 0.01) and score 2-4 (p less than 0.005) group. JGRPC and Gleason's classification are thought to be equally useful in estimating prognosis of prostatic cancer, but the former is more concise and easily applicable than the latter.