End-stage renal disease (ESRD) is more frequent in African Americans (blacks) compared to whites. Because renal fibrosis is a correlate of progressive renal failure and a dominant feature of ESRD, and because transforming growth factor beta 1 (TGF-beta1) can induce fibrosis and renal insufficiency, we hypothesized that TGF-beta1 hyperexpression is more frequent in blacks compared to whites. We measured circulating levels of TGF-beta1 in black and white patients with ESRD, hypertension, and in normal patients. We demonstrated that circulating levels of TGF-beta1 are higher in black ESRD patients, hypertensive patients, and normal control patients compared to their white counterparts. Our preliminary genetic analyses suggest that TGF-beta1 DNA polymorphisms are different in blacks and whites. Our observations of hyperexpression of TGF-beta1 in blacks suggest a mechanism for the increased prevalence of renal failure and hypertensive target organ damage in this population.