The pathways of arachidonic acid metabolism are becoming increasingly complex. Although it is unlikely that every pharmacological action of these eicosanoids reflects a physiological function, some of these compounds undoubtedly act as mediators of pathophysiological processes. Analogues of PGs have been exploited to a limited extent, and the emphasis for future therapeutic approaches will be on development of specific inhibitors and antagonists of eicosanoids that will alter the profile of products formed. These will be in the areas of inflammation (including asthma), cytoprotection of gastric mucosa, ischaemic protection and reperfusion injury, prevention of vascular disease, and human and animal reproduction. Because of the broad range of biological functions in which eicosanoids are involved, it is difficult to predict upon which of these areas new drugs will have the greatest impact.