Transforming growth factor-beta1 (TGF-beta1) is known to induce progression of experimental renal disease. Here we determined whether there is an association between serum levels of TGF-beta1 and the risk factors for progression of clinically relevant renal disorders in 186 black and 147 white adults, none of whom had kidney disease or diabetes. Serum TGF-beta1 protein levels were positively and significantly associated with plasma renin activity along with the systolic and diastolic blood pressure in blacks but not whites after controlling for age, gender, and body mass index. These TGF-beta1 protein levels were also significantly associated with body mass index and metabolic syndrome and more predictive of microalbuminuria in blacks than in whites. The differential association between TGF-beta1 and renal disease risk factors in blacks and whites suggests an explanation for the excess burden of end-stage renal disease in the black population, but this requires validation in an independent cohort. Whether these findings show that it is the circulating levels of TGF-beta1 that contribute to renal disease progression or the findings reflect other unmeasured factors, further longitudinal studies are needed.