Background/Aim of the study: The periprosthetic or superficial site infections are one of the most catastrophic and difficult to manage complications following total hip arthroplasty. Recently, in addition to well know systemic markers of inflammation, the blood and synovial fluid biomarkers are focused to have a possible role in the infection diagnosis. The long Pentraxin 3 (PTX3) seems to be a sensitive biomarker of acute phase inflammation. The objectives of this prospective and multicentre study were (1) to establish the plasma trend effectiveness of PTX3 in patients undergoing primary hip replacement, and (2) to evaluate the diagnostic accuracy of blood and synovial PTX3 in patients undergoing prosthetic revision of infected hip arthroplasty.