Both central and upper-body adiposity are associated with high rates of type II non-insulin-dependent diabetes mellitus (NIDDM), high triglyceride levels, and low high-density lipoprotein (HDL) cholesterol levels. Previous data have also suggested that central and upper-body adiposity are relatively uncorrelated and hence may measure different aspects of regional body fat distribution. We assessed body mass index (BMI), the ratio of subscapular-to-triceps skinfold (STR), the ratio of waist-to-hip circumference (WHR), lipids, lipoproteins, and glucose tolerance in 738 Mexican Americans (ages 25-64 yr), who participated in the San Antonio Heart Study, a population-based study of diabetes and cardiovascular risk factors. NIDDM was diagnosed according to National Diabetes Data Group criteria. In general, STR and WHR were associated with high NIDDM rates, low HDL cholesterol levels, and high triglyceride levels, although WHR was somewhat more predictive of these than STR. In females, BMI, WHR, and STR all made independent contributions to prediction of NIDDM and HDL cholesterol; in males, WHR and STR both made independent contributions to prediction of triglyceride levels. This suggests that both indices may measure different aspects of body-fat distribution. Investigators should consider measuring both of these indicators of body-fat distribution in studies of diabetes and other cardiovascular risk factors, although if only a single measure is feasible, WHR appears to be preferable.