The authors postulated that as Mexican Americans became more affluent and/or acculturated to "mainstream" United States life-style they would progressively lose their "obesity-related" pattern of cardiovascular risk factors which were defined as: obesity, diabetes, hypertriglyceridemia and low levels of high density lipoprotein cholesterol. This hypothesis was tested in 1979-1982 in the San Antonio Heart Study, a population-based study on 1,288 Mexican Americans and 929 Anglos living in three San Antonio neighborhoods: a low-income barrio, a middle-income transitional neighborhood, and a high-income suburb. The study population comprised 25-65-year-old men and nonpregnant women. In Mexican American women, all of the "obesity-related" risk factors fell sharply with rising socioeconomic status. In Mexican American men, by contrast, diabetes was the only "obesity-related" risk factor which fell with rising socioeconomic status. Moreover, it fell less steeply, there being an approximately twofold difference in diabetes prevalence between the barrio and the suburbs in men compared to a fourfold difference in women. Also, total and low density lipoprotein cholesterol rose with rising socioeconomic status in Mexican American men, but not in Mexican American women. "Obesity-related" risk factors were generally higher in Mexican Americans of both sexes than in their Anglo neighbors who were of similar socioeconomic status. These results suggest that cultural factors exert a stronger influence on diabetes and cardiovascular risk factors in Mexican Americans than do purely socioeconomic factors.