Histologic analysis was performed of bile duct tissue from 15 patients who underwent treatment for malignant obstructive jaundice with a self-expandable stent. Stents were in place from 5 days to 21 months. Malignancies included adenocarcinoma of the pancreas or gallbladder or cholangiocellular, hepatocellular, or gastric carcinoma. Stents were blocked by sludge in two cases and tumor overgrowth in two others. Microscopic evaluation showed that stent placement caused complete denudation of the mucosa and mild submucosal inflammation with edema. In all but one patient, the stent was incorporated into the bile duct wall and was covered by a fibrogranulomatous tissue layer after 2 months. In some cases, an epithelium-like cell formation covered the inner surface of the stent. Tumor ingrowth was observed in two patients with poorly differentiated tumors. In stents placed for longer than 2 months, mild to moderate fibrosis and foreign body reaction were observed. Hyperplastic biliary epithelium was not found within the stent or at the stent ends.