Background: The efficacy and complications of covered self-expandable metal stents (SEMS) remain controversial. Objective: We conducted this study to compare the efficacies and complication rates of covered and uncovered SEMS in malignant biliary obstruction. Design: Data on patients who underwent endoscopic retrograde biliary drainage with covered or uncovered Wallstents for the palliation of unresectable distal malignant biliary obstruction were collected. Stent patency, complications, and causes of stent occlusion were analyzed. Setting: We collected the data retrospectively. Patients: A total of 77 patients received Wallstents for unresectable distal malignant biliary obstruction. Interventions: Endoscopic sphincterotomy was performed, and a Wallstent was deployed after guidewire passage. Polyurethane-covered Wallstents were used in 36 patients and uncovered Wallstents in 41 patients. Results: Stent migration occurred in 3 of the covered Wallstent group and in 1 of the uncovered Wallstent group. Cholecystitis occurred in 1 of the covered Wallstent group but in none of the uncovered Wallstent group. Stent occlusion occurred after a mean of 398 days in the covered group and after 319 days in the uncovered Wallstent group (P > .05). Stent patency rates were 83%, 78%, 67%, and 54% at 100, 200, 300, and 400 days, respectively, in covered group and 83%, 66%, 54%, and 36% in the uncovered group, which was not significantly different. Limitations: This study is not a prospective randomized study and sample size is not large. Conclusions: Covered Wallstents are safe with acceptable complication rates. However, we found no significant difference between the stent patencies of covered and uncovered Wallstents.