OBJECTIVE The purpose of this study was to determine the extent to which the incidence of endometrial cancer in Chinese, Japanese, and Filipino residents of the United States varies according to country of birth. METHODS Women 35-74 years diagnosed with endometrial cancer between 1973 and 1986 among residents of the San Francisco/Oakland (CA) metropolitan area, 13 counties of western Washington, and the state of Hawaii were identified by cancer registries serving these populations. From a special tabulation of the 1980 US census, we estimated the size of the population at risk in each of these three areas according to age, race, and country of birth. RESULTS The annual incidence of primary endometrial cancer was lower among Chinese-American (42.6/100,000) and Japanese-American (25.3/100,000) women born in Asia than among their counterparts who were born in the United States (57.2/100,000 and 51.2/100,000, respectively). No difference in incidence was observed between Filipino women born in Asia (27.4/100,000) and those born in the United States (25.4/100,000). The rate of endometrial cancer among US-born white women (77.0/100,000 women years) exceeded that in any of these Asian-American subgroups. CONCLUSIONS These findings suggest that some clues to the aetiologies of endometrial cancer may be found in exposures whose prevalence differs between generations of Chinese and Japanese Americans.