Osteoclast Associated Receptor (OSCAR) is a novel member of leucocyte receptor complex (LCR)-encoded family expressed by pre-osteoclasts and mature osteoclasts (OC). Blocking of OSCAR binding to its putative ligand has been shown to inhibit osteoclast formation. To date there is no data available regarding the expression of OSCAR in tissues associated with osteolysis and the objective of this study is to determine if OSCAR is expressed adjacent to focal bone osteolysis near failed implants. A total of 22 samples (10 Peri-implant tissue and 12 OA) were studied. OSCAR antibodies were a gift from R& D Systems Inc. (Minneapolis, MN, USA). The tissues were analysed semi-qualitatively using semi-quantitative scoring (SQA) independently by two observers. Non-parametric Mann Whitney-U test was used to test statistical significance. Dual labelling for OSCAR and CD68 expression was also carried out. Strong expression of OSCAR was seen in the majority of multinucleated cells in peri-implant tissues while OA tissues showed very low levels of OSCAR expression. Dual labelling studies revealed that the cells expressing OSCAR also expressed CD68. There was a significant difference in the expression of OSCAR between peri-implant tissue and OA synovial tissue (p< 0.003). This study shows that OSCAR is expressed at high levels by the numerous CD68 multinucleated cells present is these tissues in peri-implant tissues. These findings and recent reports on the role OSCAR may play in OC formation indicate that OSCAR could be an important mediator of peri-implant osteolysis