Four patients with acquired immunodeficiency syndrome (AIDS) (CDC group IV) were investigated for biliary disease because of the presence of both severe upper abdominal pain and raised levels of serum alkaline phosphatase. None was clinically jaundiced. Upper abdominal ultrasound was abnormal in three. All had endoscopic retrograde cholangiographic evidence of both an intrahepatic sclerosing cholangitis suggestive of primary sclerosing cholangitis and an irregular suprapapillary common bile duct dilation suggestive of papillary stenosis. Three had evidence of gastrointestinal cryptosporidiosis and two of disseminated cytomegalovirus infection. Endoscopic sphincterotomy, performed in two patients, gave good pain relief. We propose the name 'AIDS sclerosing cholangitis' for this form of secondary cholangitis. The cause of this disorder remains unclear. Recent evidence is discussed which suggests that it is not due to HIV itself but to an opportunistic infection. Cryptosporidium appears to be the most likely candidate. © 1988 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.