Previous investigations have established that the Mexican-American community of south Texas has a three- to five-fold elevated risk for non-insulin dependent diabetes mellitus when compared to the US population as a whole. In addition, evidence points to similarly increased risks of the related disorders, hypertension and obesity. In this paper, age- and sex-specific rates of borderline and definite hypertension among 1931 Mexican-Americans aged 15 years and above based on a single, at-home blood pressure determination are reported. Observed rates of definite hypertension are uniformly lower than the US population while borderline hypertension is correspondingly higher for all age and sex strata yielding overall prevalences of hypertension which are not significantly different. The Starr sample, however, has one and one-third times as many individuals taking hypertensive medications so that the true rate of hypertension is likely to be higher. Examining sources of blood pressure variability using analyses of covariance indicate that age has the most significant effect. A direct measure of body size was not available, but classification based on simple silhouettes representing body form is shown to be the next most significant effect. Furthermore, the silhouettes appear to provide nearly an equivalent amount of information as does the body mass index as an empirical predictor of blood pressure variability. Diabetic classification is a significant effect for systolic blood pressure in females, but not for males or for diastolic pressure in either.