Introduction: Overview of periprocedural and postprocedural (early and late) complication giving us access to determine the biological eff ects of treatment with covered versus uncovered metal stents in patients with irreversible jaundice malignant etiology. The Aim: The aim of study was to compare the clinical therapeutical eff ects of covered billiary stents versus uncovered billiary stents. Subjects and methods: We treated two groups of patients with irreversible cholestasis malignant etiology. In the fi rst group of patients were used metal covering stents (MCS), while in the other group used metal uncovered stents (MNS). Results: We observed periprocedural complications, technical complications, and the early-to 30-day and late-to 6 months post-procedural complications such as parameters of biocompatibility of inserted endoprosthesis, i.e. biological eff ects on surrounding tissues. We found statistically high diff erence in the occurrence of bleeding and periprocedural complications in total of MNS group. In the category of early postprocedural complications, we found a statistically signifi cant diff erence in the MNS groups for a hemobilia, post-stent cholangitis, stent occlusion, irritative symptoms and appetite loss, and also in the overall appearance of early postprocedural complications in MNS. In the category of late postprocedural complications statistically signifi cant diff erence we found in the MNS reobstructive cholangitis, reobstruktive jaundice, irritative symptoms, loss of appetite and in full. The cause of stent dysfunction-obliteration, biliary encrustation, ingrowth, overgrowth and mucosal hyperplasia, tells us in favor of the biological eff ects of the insertion, point applied prosthesis and the fi nal therapeutic eff ect achieved by them. Conclusions: According to our results, taking into account the parameters of biocompatibility under applicable defi nitions, authors can conclude that covered stents in contrast to the uncovered are meeting the criteria of almost ideal biological prostheses.