A lower cardiovascular mortality in Mexican-American men than in non-Hispanic white men has been consistently observed. In contrast, no such ethnic difference has been observed in women. To determine whether this sex-ethnicity interaction in mortality is matched by a corresponding sex-ethnicity interaction in cardiovascular risk factors, the authors compared risk factors between 3,301 Mexican Americans and 1,877 non-Hispanic whites from the San Antonio Heart Study, a population-based study of cardiovascular disease and diabetes conducted in San Antonio, Texas (1979-1988). In both men and women, triglycerides, systolic and diastolic blood pressures, and body mass index (weight (kg)/height (m)2) were higher and high-density lipoprotein cholesterol was lower in Mexican Americans than in non-Hispanic whites. Although Mexican-American men were more likely than non-Hispanic white men to be smokers, Mexican Americans of both sexes smoked, on average, fewer cigarettes per day than non-Hispanic whites. Cardiovascular risk scores, which were constructed from Framingham Study risk equations to summarize the combined effect of multiple risk factors, were higher in Mexican Americans than in non-Hispanic whites of both sexes. The cardiovascular risk profile was less favorable for both Mexican Americans who grew up in Mexico and Mexican Americans who grew up in San Antonio. Although it is possible that in their younger years Mexican Americans had a more favorable cardiovascular risk profile, these results may also indicate that some protective factor, either genetic or life-style, is present in Mexican-American males but absent in non-Hispanic white males.