Numerous lines of evidence, including upregulation of TGF-β signaling in the glomerulus or tubulointerstitium, increased TGF-β-induced renal fibrosis, and amelioration of renal fibrosis through anti-TGF-β treatment, support the role of TGF-β in fibrosis associated with kidney diseases. The gene discussed is TGFB1; the disease is renal fibrosis.