Congenital hepatic fibrosis (CHF) is an important cause of morbidity and mortality in patients with Autosomal Recessive Polycystic Kidney Disease (ARPKD). The pathogenesis of CHF remains undefined. Several recent studies suggest that the reninangiotensin system (RAS) is an important mediator of progressive hepatic fibrosis, through activation of pro-fibrotic mediators, such as transforming growth factor-β (TGF-β). RAS activation has not previously been studied in CHF patients or animal models. The aim of the current study was to characterize RAS expression during the course of CHF in the PCK rat.