The cytokines interleukin-1 and tumor necrosis factor contribute to the pathogenesis of inflammatory diseases and, potentially, to atherogenesis. The synthesis of these cytokines in humans can be suppressed by oral intake of n-3 polyunsaturated fatty acids. This mechanism may contribute to the beneficial effect of long-term n-3 fatty acid supplementation in inflammatory diseases such as renal transplant rejection, immunoglobulin A nephropathy and rheumatoid arthritis.