In our department, hepatorenal syndrome was highly associated with obstructive jaundice and was seen in 9.2 percent of patients with obstructive jaundice. This syndrome developed when in underlying hepatic disease, acute renal failure supervened. Histological findings of renal failure caused by obstructive jaundice were summarized as tubular necrosis and the presence of protein-like substance in the glomerulus, which were mostly reversible and similar to those seen in shock. To investigate the pathogenesis of hepatorenal syndrome, experimentally the common duct in dog was ligated to produce obstructive jaundice and B. Klebsiella was injected into the bile duct to produce cholangiolitis. From this study, it was evident that cholangiolar infection was closely correlated with the manifestation of renal failure. In fact, without acquiring infection, renal failure did not occur. Moreover, this infection produced endotoxemia with high incidence. Therefore, it is assumed that this cholangiolar infection plays an important role in the pathogenesis of hepatorenal syndrome caused by obstructive jaundice.