Although heat shock protein 72 kDa (HSP72) protects tubular epithelium from a variety of acute insults, its role in chronic renal injury and fibrosis is poorly characterized. In this study, we tested the hypothesis that HSP72 reduces apoptosis and epithelial to mesenchymal transition (EMT), important contributors to tubular cell injury in vitro and in vivo. In rats, orally administered geranylgeranylacetone (GGA), an agent that selectively induces HSP72, markedly reduced both apoptosis and cell proliferation in tubular epithelium and decreased both interstitial fibroblast accumulation and collagen I deposition after unilateral ureteric obstruction (UUO), a model of chronic renal tubulointerstitial fibrosis and dysfunction. In cultured renal NRK52E cells, exposure to TGF-1 induced EMT and apoptosis, major causes of renal fibrosis and tubular atrophy, respectively. Exposure to a pan-caspase inhibitor (ZVAD-FMK) prevented TGF-1-induced apoptosis but did not reduce EMT. In contrast, selective HSP72 expression in vitro inhibited EMT caused by TGF-1 as indicated by preserving E-cadherin expression level and -smooth muscle actin (-SMA) induction. siRNA directed against HSP72 blocked the cytoprotective effects of HSP72 over-expression on EMT in TGF-1 exposed cells. Taken together, our data indicate that HSP72 ameliorates renal tubulointerstitial fibrosis in obstructive nephropathy by inhibiting both renal tubular epithelial cell apoptosis and EMT.