This study examines the extent to which various ethnic-immigrant and US-born groups differ in their risks of all-cause and cause-specific mortality, morbidity, and health behaviors. Using data from the National Longitudinal Mortality Study, 1979-1989, we estimated, for major US racial and ethnic groups, mortality risks of immigrants relative to those of the US-born. The Cox regression model was used to adjust mortality differentials by age, sex, marital status, rural/urban residence, education, and family income. Logistic regression was fitted to the National Health Interview Survey data to determine whether health status and behaviors vary among ethnic-immigrant groups and by length of US residence. Compared with US-born whites of equivalent socioeconomic and demographic background, foreign-born blacks, Hispanics, and Asians/Pacific Islanders (APIs), US-born APIs, US-born Hispanics, and foreign-born whites had, respectively, 48%, 45%, 43%, 32%, 26%, and 16% lower mortality risks. While American Indians did not differ significantly from US-born whites, US-born blacks had an 8% higher mortality risk. Black and Hispanic immigrants experienced, respectively, 52% and 26% lower mortality risks than their US-born counterparts. Considerable differentials were also found in mortality for cancer, cardiovascular, respiratory, infectious disease, and injury, and in morbidity and health behaviors, with API and Hispanic immigrants generally experiencing the lowest risks. Consistent with the acculturation hypothesis, immigrants' risks of smoking, obesity, hypertension, and chronic condition, although substantially lower than those for the US-born, increased with increasing length of US residence. Given the substantial nativity differences in health status and mortality, future waves of immigrants of diverse ethnic and cultural backgrounds will likely have a sizeable impact on the overall health, disease, and mortality patterns in the United States.