Platelet activating factor (PAF) is a unique phosphoglyceride which possesses many potent biological activities relevant for the pathogenesis of diseases of the elderly. PAF is generated and released by numerous cell types and tissues and is rapidly metabolised through a well defined metabolic cycle. Its biological actions are mediated via direct and indirect stimulatory effects on target cells and tissues. The current knowledge of PAF and its role in cardiovascular disease, thromboembolism, cerebral ischaemia and neurodegenerative disorders are discussed in detail. It is likely, that in future, a better understanding of the pathophysiological and physiological roles of PAF will provide new strategies for the treatment of human diseases of aging.