Summary:The process of ultrahigh molecular weight polyethylene (UHMW-PE) breakdown, started at the articular surface of the cup, continues in small fragments after generation. An assiduous interaction between the UHMW-PE particles and the host cells leads to oxidative changes of the UHMW-PE and to size reduction of the particles simultaneous with transporting them toward, and finally by, lymphatic or blood vessels. The particles are mobilized by means of enzymatic, extracellular matrix-degrading activity of cells that have phagocytosed them or adhered to them. Together, these characteristics indicate an attempt by the natural cellular immunity system to eliminate the implant wear debris. Macrophages are the main effector cells acting as scavengers; however, excessive amount of the wear debris evokes phagocytic activity of cells other than macrophages as well.