The potentially severe complications related to metal-on-metal (MoM) hip replacements have led to a dramatic decrease of their use. Large diameter heads are more likely to fail than smaller diameters, but complications have been described even with « small » diameters. Therefore, monitoring of MoM arthroplasties is mandatory. This includes physical examination, X-Rays, metal ion levels, and potentially cross-sectional imaging. Despite pathophysiology of adverse reactions to metal debris (ARMD) is better understood, their evolution and the potential systemic complications remain unclear. Symptomatic hip arthroplasties, elevated ions levels, and ARMD may lead to revision of the components. In such a situation, an adaquate stategy must be achieved given the high potential for complications.