Platelet-activating factor (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine [PAF]) is a potent lipid autocoid produced by many cell types. PAF is produced by cultured rat cerebellar neurons and human fetal brain cells, and has been extracted from brain tissue. Multiple PAF receptors have been demonstrated in brain tissue. PAF stimulates intracellular Ca2+ mobilization and phosphatidylinositol (PI) metabolism in transformed neuronal cell lines via the PAF receptor, to which both pertussis toxin (PTX)-sensitive and -insensitive G protein appear to couple. PAF has potent actions on cerebral vessels and cerebral metabolism when administered in vivo. Direct neuronal effects of PAF, such as inhibition of acetylcholine release, are observed in vitro. Excessive PAF production in pathological states of the nervous system, such as neurotrauma and stroke, has been shown. In multiple studies in rodent and non-rodent models using highly specific and potent PAF antagonists, reversal or prevention of key consequences of brain injury, such as hypoperfusion following ischemia, reperfusion and edema, inflammatory cell accumulation, neurologic/motor deficits, and neuronal salvage, has been demonstrated. These studies taken together support a role for PAF as an important mediator in the pathophysiology of brain injury.