C-reactive protein (CRP) is the prototype of acute-phase protein which is secreted by the liver in response to a variety of inflammatory cytokines. Levels of CRP can increase up to 1000-fold very rapidly after the onset of inflammation and decrease just as rapidly with the resolution of aggression. CRP is a member of the ancient highly conserved pentraxin family of proteins and it is arranged in a cyclic homopentameric structure. The important role of CRP in innate immunity is largely due to its opsonizing abilities, its capability to activate human complement and to bind to immunoglobulin G receptors. CRP can bind phosphocholine largely present in bacterial membranes, cell membrane and lipoproteins, in addition CRP can recognize nuclear constituent in damaged cells. CRP can activate C3 convertase through the classical pathway but not C5 convertase resulting in generation of opsonic complement fragments. Interactions of CRP with Fc receptors lead to the generation of proinflammatory cytokines and reactive oxygen species by monocyte/macrophage while inhibit neutrophiles functions. Recently, CRP was demonstrated to play an active role in atherogenesis and it has been largely proven that a microinflammatory state as defined by a moderate increase in CRP (up to 3 mg/l), is associated with an increased risk for arterial disease. Moreover it has been postulated that CRP may be a useful tool for monitoring drug therapy.