Prolonged cholestasis was observed in 6 children with histiocytosis X. Operative cholangiograms confirmed the patency of the extrahepatic biliary tree and showed marked distortion of intrahepatic bile ducts resembling that observed in sclerosing cholangitis. Histologic examination showed portal fibrosis in all patients; only one was found to have portal histiocytic infiltration. The subsequent course confirmed the ominous significance of cholestasis in histiocytosis X, a rare finding in this disease: One patient died of progressive liver failure and three others from sepsis after unsuccessful attempts to improve the condition of the liver with chemotherapy.