The systematic use of metallic stents (MS) is hampered by their price compared to plastic stents (PS) in biliary obstruction. Aims. 1- to compare cost and efficacy of plastic stents (PS) and metallic stents (MS) in the treatment of inoperable malignant strictures of the common bile duct, 2- to define predictive factors of survival of patients with inoperable malignant biliary stricture. Patients. 118 patients (mean age 75 yrs) with an inoperable malignant stricture of the common bile duct were randomized to receive PS or MS. The characteristics of the 2 groups were comparable. Comparisons were made with chi-2 tests and survival rates compared with a Cox model. Results. There was no significant difference of survival between the 2 groups. Time for first obstruction was longer in patients with PS (median not reached vs 5 months, p=0.007). Number of additional days of hospitalization (173), of days with antibiotics (237), of ERCPs (20) and of abdominal ultrasonographies (18) were significantly higher in the group treated with PS. By multivariate analysis, 2 variables were independent prognostic factors of survival: the ASA classification (p=0.03 ; RR=1.5) and the number of liver metastases (p<0.0001 ; RR=1.5). Combination of these 2 variables allowed to define a group with a short survival (1.9 months) and another group with a longer survival (5.6 months) in which the overall cost of MS was lower than that of PS. Conclusions. MS are more effective for treatment of inoperable malignant stricture of the common bile duct. Combination of 2 predictive prognosis factors (ASA and number of liver metastases) allows to define the best type of stent according to the estimated survival time of patients.