Background: The efficacy of polyurethane-covered metal expandable stents for treatment of neoplastic distal biliary obstruction was analyzed. Methods: Twenty-one patients with unresectable malignant tumors involving the mid to distal bile duct who were seen with obstructive jaundice were consecutively enrolled. Eighteen patients underwent endoscopic implantation of a polyurethane-covered metal stent and 3 patients underwent transhepatic insertion because of duodenal obstruction. The stent patency, complications, and patient survival were analyzed. Results: Effective biliary decompression was achieved in all patients. Adverse events were minor: mild pancreatitis (1) and cholecystitis (2) occurred within 7 days of stent insertion. Mean survival and stent patency were 233 days and 206 days, respectively. Stent occlusion occurred in 3 patients (14%) after a mean of 188 days. Tumor ingrowth through the stent mesh was not observed. However, 2 stents were occluded by tumor overgrowth and 1 by compacted alimentary debris. Conclusions: A polyurethane membrane may prevent tumor ingrowth and reduce the occlusion rate for expandable metal stents implanted in patients with malignant obstruction of the distal bile duct. (Gastrointest Endosc 2002;55:366-70.)