By comparison with other human organs, relatively detailed studies of the pathogenic significance of chemical mediators of inflammation may be carried out in the skin. The pro-inflammatory effects of certain mediators may easily be determined. Such mediators may be recovered from inflammatory processes in human skin, quantified in a controlled manner, and the pharmacological and clinical effects of specific enzyme inhibitors determined, in vivo. Several biologically active metabolites of arachidonic acid, including prostaglandins E2 and D2′ leukotrienes B4′ C4 and D4′ and 12-hydroxyeicosatetraenoic acid have been the subjects of such studies, which are reviewed. The family of polypeptides known as interleukin-1 are also emerging as inflammatory mediators of potential importance in the skin.