BackgroundFew data are available on the prevalence of hypertension in Mexico.Methods and ResultsWe compared the prevalence of mild hypertension (systolic blood pressure ≥140 mm Hg and/or diastolic blood pressure ≥90 mm Hg and/or use of antihyper-tensive medications) in 1500 low-income Mexican Americans who participated in the San Antonio Heart Study and 2280 low-income Mexicans who participated in the Mexico City Diabetes Study. The crude prevalence of mild hypertension was 17.1% in Mexican men versus 24.4% in Mexican American men (P=.001) and 17.4% in Mexican women versus 22.0% in Mexican American women (P=.005). After adjustment for age, body mass index (BMI), waist-to-hip ratio (WHR), non-insulin dependent diabetes mellitus (NIDDM), educational attainment, and percent native American genetic admixture (Caucasian and native American), the odds ratio (Mexico City/San Antonio) was 0.55 (95% CI, 0.39, 0.77;P<.001) in men and 0.81 (CI, 0.54, 1.12;P=.201) in women. In a pooled model including both men and women, the odds ratio was 0.67 (95% CI, 0.53, 0.84;P<.001). In the pooled model, city, age, female sex, NIDDM, BMI, WHR, and low educational attainment were significantly related to the prevalence of hypertension.ConclusionsThe causes for these differences in hypertension prevalence are not known but may reflect a less modernized lifestyle in Mexico City, including greater physical activity, less obesity, and the consumption of a high-carbohydrate, low-fat diet.