Japanese men in Hawaii whose ancestral roots were in Okinawa were compared to Japanese migrants from all other prefectures. The Okinawan migrants have acquired fewer cancers than men from other prefectures (P = 0.12). No one primary site accounts for this difference. Stomach cancer rates showed the largest difference between the two migrant groups. This replicates the experience of Okinawans and non-Okinawans in Japan itself. Lymphosarcoma mortality rates are much higher in Okinawa than in all Japan, but this difference is not reproduced in Hawaiian migrants. This could be explained by a post migrational decrease in HTLV-I-related acute T-cell lymphoma/leukemia. Cancer of the mouth, pharynx and esophagus has decreased in all Japanese migrants, but the decrease is much greater among Okinawan migrants, suggesting they have escaped exposure to risk factors peculiar to the Okinawan environment. Colon cancer is more common in migrant Japanese than in U.S. whites. The dramatic increase in the frequency of this tumor affects Okinawan and non-Okinawan migrants to an equal degree.