BACKGROUND: Most patients with malignant common bile duct strictures are suited only for palliation of jaundice by placement of a polyethylene (PE) stent using an endoscopic retrograde cholangiographic technique. Occlusion of these stents occurs after 3 to 4 months, whereas uncovered self-expanding metal stents (SEMS) remain open twice as long. The initial higher cost of the latter might be balanced by a decreased need for repeat intervention. OBJECTIVE: To compare the patency of 10F PE stents and covered 30F steel SEMS (Wallstent; Boston Scientific Nordic AB, Helsingborg, Sweden). DESIGN: Single-center, prospective, randomized, controlled trial. SETTING: General hospital in Stockholm, Sweden, which has a catchment area of 0.6 million people. PATIENTS: Non-referred, unresectable malignant common bile duct strictures. INTERVENTIONS: Endoscopic retrograde cholangiography with plastic stents or covered SEMS. MAIN OUTCOME MEASUREMENTS: Time to stent failure, requiring a new stent. LIMITATIONS: Similar setting and patients, and costs in Scandinavia. RESULTS: Fifty-one and 49 patients were allocated to the PE stent and SEMS groups, respectively. Fifty-six patients died without stent failure within 10 months (median, 2.6 months). Twenty-two PE stent and 9 SEMS patients (P = .009) developed failure after a median of 1.1 and 3.5 months, respectively (P = .007). Median patency times were 1.8 and 3.6 months in the PE and SEMS groups, respectively (P = .002). Median survival was 4.5 months; in 35 patients with distant metastases, the median survival was 2.5 months (P = .002)(PE group, 1.9 months). CONCLUSIONS: The more-effective SEMS are recommended in unresectable patients with malignant common bile duct strictures, who survive a median of 4.5 months. Less costly plastic stents are preferable in the one third of patients who have distant metastases. In our study, the cost was equal.