Primary sclerosing cholangitis is a progressive, cholestatic hepatic disease of unknown etiology. It is characterized by progressive inflammation, destruction, and fibrosis of the intrahepatic and extrahepatic bile ducts. Several medical therapies have been tried such as penicilamin, colchicine, methatraxate, cyclosporine, tacrolimus, and ursodeoxycholic acid. Treatment with mucolytic agents in excessively high viscosity conditions appears to have an important role. N-acetylcysteine (NAC), as a mucolytic agent, may fascilitate the drainage in partial obstructions by decreasing the mucous viscosity. We suggest that NAC and ursodeoxycholic acid have markedly positive effects on the clinical course of cholangitis and cholestasis when used together by affecting bile viscosity. Here, we present two cases treated with NAC. NAC capsul therapies at 800 mg/day were administered to two patients with primary sclerosing cholangitis. Clinical and laboratory parameters of patients saw significant improvement.