Osteoprotegerin (OPG) is a soluble glycoprotein, mainly involved in bone metabolism, but it is also found in various other tissues like vascular smooth muscle cells. Osteoprotegerin has been implicated in various inflammations and has additionally been linked to diabetes mellitus, silent myocardial ischemia, acute myocardial infarction, and left ventricular dysfunction. Receptor activator of nuclear factor kappa-B (RANK), RANK ligand (RANKL), and OPG represent an interesting putative pathway in vascular remodeling and atherosclerotic disease. OPG acts as a decoy receptor for RANKL. This study was performed to investigate the role of RANKL and OPG and their relative ratio (RANKLOPG) in pathogenesis of ACS, as well as to study the differences in median serum levels of RANKL, OPG and RANKL / OPG ratio according to some demographic and clinical features.