Hemobilia is defined as hemorrhage into the biliary tract, and the patients with hemobilia present with abdominal pain, jaundice and gastrointestinal bleeding. The causes of hemobilia are traumatic or operative injury to the liver or bile ducts, intraductal rupture of the hepatic abscess or aneurysm of the hepatic artery. Cholecystitis can also develop in patients with hemobilia. Polyarteritis nodosa (PAN) is a multisystem, necrotizing vasculitis of the small and medium-sized muscular arteries and patients with this illness may present with fever, sweats, weight loss, severe arthralgia and myalgia. Mesentery artery involvement that can result in gastrointestinal hemorrhage, bowel infarction and perforation is rare, yet very serious in patients with PAN. We report here on a rare case of PAN that presented as hemobilia due to rupture of a hepatic arterial aneurysm. (Korean J Gastrointest Endosc 2009;38:364-367)