A statistical analysis was made by computer on 511 cases of testicular tumor experienced at 14 facilities in Japan between 1970 and 1979. The age distribution of the patients had two peaks, one under 3 years (15%) and the other between 25 and 34 years (32%). Forty percent of the patients were office workers and 76% were college graduates. Fifty percent of the patients had 0 to 1 sibs. The blood type distribution was similar to that for the whole Japanese population. Six percent of the patients had a past history of trauma, and no relation with cell type was detected. Sixty nine percent of the patients were married and 31% were not married. Sixty seven percent of the patients over 30 had seminoma, and 78% of the patients under 29 years old had non-seminoma. Seminoma was rare in patients under 9 years old. Histologically, 75% were simple type, and 25% were mixed type. Forty three percent of the cases were seminoma and 57% were non-seminoma. Of the stage I cases, 78% and 57%, and of the stage III cases 7 and 28%, respectively, were seminoma and non-seminoma, many of the non-seminoma being at high stage. The 5-year survival rate for the 75 patients under 9 years old was 96%, and that for the 341 patients over 15 years was 70%, the survival rate for the patients under 9 years being significantly higher. The 5-year survival rate for stage I, II and III seminoma was 100, 65 and 0%, respectively, while that for non-seminoma was 93, 56 and 8%, respectively. The survival rate for stage I was higher for seminoma cases than for non-seminoma cases. No difference was detected between survival rate for stage II or III between seminoma and non-seminoma. The survival rate for seminoma did not differ with the time when the surgery was performed, but for the patients with non-seminomatous tumors, the survival rate was higher for the patients operated within one month than those operated later. The survival rate was not related to the weight of the extracted testicle. The 5-year survival rate for the patients with normal body temperature was 78% whereas that for the patients who had fevers was 32%. The 5-year survival rate for the patients not accompanied by abdominal tumors was about 80%, whereas that for the patients with palpated abdominal tumors was 42%.(ABSTRACT TRUNCATED AT 400 WORDS)