Endoscopic retrograde cholangiopancreatography (ERCP) was performed in twenty-six AIDS patients to evaluate either abdominal pain suggestive of biliary tract disease, fever, serum alkaline phosphatase elevation, or a combination of these findings. Twenty patients (77%) had abnormal cholangiograms and four distinct patterns were identified: (1) papillary stenosis (n = 3); (2) sclerosing cholangitis (n = 4); (3) sclerosing cholangitis with papillary stenosis (n = 10); and (4) long extrahepatic bile duct strictures (n = 3). Ampullary biopsy and culture identified an AIDS-related pathogen (CMV, MAI and cryptosporidium) or malignancy (lymphoma, Kaposi's sarcoma) in eleven patients (55%). No features differentiated patients with normal from patients with abnormal cholangiograms. Noninvasive biiary tract imaging studies (CT, ultrasound), however, showed ductal dilation in 75% of patients with abnormal cholangiograms compared with 16% in those with normal cholangiograms (p <0.001). Endoscopic sphincterotomy (ES) in 12 patients with either papillary stenosis or the combination of sclerosing cholangitis and papillary stenosis produced a significant reduction in right upper abdominal pain, although serum alkaline phosphatase continued to increase (mean follow-up = 3.9 months). Ten of the 12 patients undergoing ES had sclerosing cholangitis, perhaps explaining this lack of response of the serum alkaline phosphatase. Of the 12 patients who had ES, five died of AIDS-related complications within nine months of the procedure (a mean of 4.8 months), four were lost to follow-up by four months, and three were alive at 12 months. Of the eight patients who did not have ES, five were alive at one to six months and three died within five months (mean 1.7 months) after the procedure. This paper expands our knowledge of biliary tract abnormalities in HIV-infected individuals and suggests that ES may improve biliary tract associated abdominal pain.