The death rate from malignant tumors of the testis in Japan has risen from 1.53 per million per year in 1947–49 to 3.81 in 1966–70. This rise has been most marked in young adults and children, where the death rate is now greater than in the U.S. white population. Fatal testicular tumors in Japanese boys occur at a younger age than in U.S. white boys. The increase in the Japanese mortality rate cannot be associated with particular years in the total period studied, but rather appears to be related to increased lifetime risks with successively later years of birth.