['Although the combination of biliary and duodenal self-expandable metal stents (SEMS) is useful, the exacerbating effect of duodenal SEMS placement on biliary SEMS has not been documented. We conducted a multicenter retrospective study to evaluate the effect of duodenal SEMS placement on biliary SEMS.', 'Patients who underwent first-time biliary SEMS placement for a distal malignant biliary obstruction between September 1994 and November 2010 were included. Time to dysfunction of biliary SEMS was analyzed to identify risk factors for biliary SEMS dysfunction. Duodenal SEMS placement was analyzed as a time-dependent covariate.', 'In total, 410 eligible patients were identified. Duodenal SEMS were placed in 33 patients (8 %). The median time to dysfunction of biliary SEMS was 170 days. Male gender (hazard ratio 1.37, 95 % confidence interval 1.03-1.83, P = 0.029) and duodenal SEMS placement (hazard ratio 2.00, 95 % confidence interval 1.16-3.45, P = 0.013) were risk factors in the multivariate Cox model. In patients undergoing duodenal SEMS, biliary SEMS dysfunction was observed in 17 (52 %) with a median time to dysfunction of 64 days after duodenal SEMS placement. As many as 60 % of the patients with biliary SEMS dysfunction after duodenal SEMS placement needed permanent percutaneous transhepatic biliary external drainage.'] Is duodenal metal stent placement a risk factor for biliary metal stent dysfunction : an analysis using a time-dependent covariate?