Possible effects of cultural variables on the risk of coronary heart disease (CHD) were examined in 7705 men of Japanese ancestry living in Hawaii. The six-year incidence of CHD was related to birthplace (Japan or elsewhere), number of years spent in Japan, ability to read and write Japanese, ability to speak Japanese, and to an index of preference for a traditional Japanese diet. Statistically significant inverse relationships were found between CHD incidence and all of these variables which reflect the degree of exposure to Japanese culture during childhood. In multivariate analyses where the major CHD risk factors were taken into account, years spent in Japan and ability to read and write Japanese remained significant. Hence, exposure to Japanese culture during childhood appears to protect against CHD in adulthood. This may explain, in part, the gradient of CHD frequency among Japanese in Japan, Japanese-Americans, and Caucasians that could not be entirely attributed to the established risk factors.