To supplement sparse data about ischemic heart disease in Asian Americans, hospitalization risk was prospectively examined in a group of Asian Americans living in Northern California. Analyses used Cox models with ischemic heart disease risk traits as covariables. With Whites as the referent category, relative risks by ethnic group were as follows: Chinese, 0.6 (P = .001); Japanese, 1.0 (P = .97); Filipinos, 1.0 (P = .95); South Asians, 3.7 (P < .001); other Asian Americans, 0.8 (P = .55). Thus, unexplained differences in ischemic heart disease risk exist among Asian-American ethnic groups, with Chinese Americans at lowest risk and persons of South Asian origin at highest risk.