The n-6 polyunsaturated fatty acid arachidonic acid gives rise to the eicosanoid family of mediators (prostaglandins, thromboxanes, leukotrienes and related metabolites). These have inflammatory actions in their own right and also regulate the production of other mediators including inflammatory cytokines. Consumption of long chain n-3 polyunsaturated fatty acids decreases the amount of arachidonic acid in cell membranes and so available for eicosanoid production. Thus, n-3 polyunsaturated fatty acids decrease production of arachidonic acid-derived eicosanoids. These fatty acids also decrease the production of the classic inflammatory cytokines tumour necrosis factor, interleukin-1, and interleukin-6 and the expression of adhesion molecules involved in inflammatory interactions between leukocytes and endothelial cells. These latter effects may occur by eicosanoid-independent mechanisms including modulation of the activation of transcription factors involved in inflammatory processes. The anti-inflammatory actions of long chain n-3 fatty acid-induced effects may be of therapeutic use in conditions with an acute or chronic inflammatory component.