Background/Aims: The necessity and efficacy of biliary drainage prior to major surgery in patients with obstructive jaundice have been reported in various clinical and experimental studies in Japan. However, it is not enough that Western countries understand the advantage of preoperative drainage. In this study, therefore, cytoprotective effect of preoperative biliary drainage was evaluated, using the cell biological technique. Materials and Methods: Ten jaundiced dogs and 10 with drainage (after induction ofjaundice) were each divided into two groups: those with and those without 40% hepatectomy. Using these four groups, the advantage of biliary drainage before hepatectomy in obstructive jaundice was studied, using isolated hepatocytes and Kupffer cells. Results: In jaundiced dogs, isolated hepatocyte viability and intracellular cyclic AIWP concentration were considerably reduced. The bleb formation rate, culture supernatant lipid peroxide and lactate dehydrogenase contents, and plasma thromboxane B-2 and 6-keto-PGF1 alpha levels all markedly in B creased. These changes were more exaggerated in those after hepatectomy. In the dogs with drainage, all of these values were approximated to those in normal animals. The changes following hepatectomy in dogs with drainage were also less pronounced in comparison with jaundiced animals. Conclusions: These findings suggest that biliary drainage prior to hepatectomy in obstructive jaundice mitigates liver impairment, both at the cellular level and in terms of prostanoid metabolism. It was concluded that preoperative biliary drainage prior to hepatectomy ensures better results for obstructive jaundice.