Platelet-derived growth factor (PDGF) and its receptors (PDGFRs) are a family of RTKs that play an important role in the regulation of normal cell growth and differentiation. PDGFRs are involved in a variety of pathological processes, including atherosclerosis, neoplasia, tissue repair, and inflammation. PDGFRs, which consist of two isoforms (alpha and beta), are membrane protein-tyrosine kinases that, upon binding to PDGF, become activated and, via recruitment of SH domain-containing effector molecules, initiate distinct or overlapping signaling cascades that coordinate cellular responses.