It has been claimed that Mexican Americans have a favorable mortality experience despite their low socioeconomic status (SES). The present study compared all-cause mortality of non-Hispanic whites with that of United States-born and foreign-born (i.e., born in Mexico) Mexican Americans. Subjects were 3735 residents of San Antonio, TX, who were followed-up for 7-8 years. The sex-age adjusted death rates per 1000 person-years were higher for United States-born Mexican Americans (5.7) than for non-Hispanic whites (3.8) or for foreign-born Mexican Americans (3.6). Foreign-born Mexican Americans had the lowest socioeconomic status (SES), and non-Hispanic whites had the highest SES. After adjustment for SES, the mortality ratio for United States-born Mexican Americans compared with foreign-born Mexican Americans was 1.9 (95% confidence interval, 1.0-3.5), while the ratio for United States-born Mexican Americans compared with non-Hispanic whites was 1.0 (95% confidence interval, 0.7-1.6). Stratified analysis revealed that those in the lowest SES tertiles had threefold greater risk of death than those in the highest tertiles among both United States-born Mexican Americans and non-Hispanic whites (test for trend, P < 0.001). These data suggest that lower SES is strongly associated with increased mortality. After adjustment for SES, mortality rates were similar for United States-born Mexican Americans and non-Hispanic whites. Foreign-born Mexican Americans had the lowest mortality rates of the three groups.