Although self-expanding metal stents (SEMS) have well-documented advantages over plastic stents (PS) for some cases of endoscopic palliation for malignant biliary obstruction, the standard practice remains variable. The aim of this study is to better stratify the key elements that aid in the choice of SEMS vs. a PS for these patients. In this study, Wallstent ® Covered Biliary Endoprostheses are compared to Amsterdam-style plastic stents for malignant obstruction of the common bile duct. The primary end-point of the study is duration of patency of the initial stent placed. Tumor type, laboratory values, quality of life measures, adjuvant treatment modalities, adverse events and clinical symptoms were tracked and analyzed at baseline and at 1, 3, 6, 12, 18 and 24 months. Eligible patients were randomized to receive either a 10F PS or the covered SEMS. 57 of a planned 120 subjects have been enrolled (28 covered SEMS, 29 PS). The demographics of both groups are similar. Malignancies include pancreatic carcinoma in 32 patients (58.2%), metastatic cancer in 11 (19.3%), ampullary carcinoma in 4 (7.3%), gallbladder carcinoma in 2 (3.6%), cholangio-carcinoma in 1 (1.8%), and 10 miscellaneous cases. To date, 50 complications have been reported: 22 in the SEMS group including 1 occlusion (at 25 days), 1 case of obstructive jaundice (305 days), and 2 cases of cholangitis. In the PS group, 28 complications have been reported including 4 occlusions (4, 9, 134 and 139 days), 1 obstruction (19 days), 3 cases of obstructive jaundice (7, 70, and 136 days), 5 cases of cholangitis, and 1 case of pancreatitis. In neither group has there been bleeding, cholecystitis, or stent migration. To date, 39 patients have reached 1-month follow-up (19 SEMS, 20 PS), and 20 reached 3-months (9 SEMS, 11 PS) follow-up. Based on available follow-up data up to 3 months, success rates for patency are 90% for the SEMS group (95% CI 55.5, 99.8) and 71.4% for the PS group (95% CI 41.9, 91.6). Results from this planned interim analysis suggest a trend for superiority of SEMS in preventing stent blockage when compared to PS in the early follow-up, in the absence of significantly increased complications such as pancreatitis or cholecystitis. Additional and longer term data are required to better determine the incidence of rarer obstructive complications, and to identify predictors that will assist clinicians in better tailoring the management of patients with lower obstruction of the common bile duct.