Omega-3 polyunsaturated fatty acids are among new treatments being tested for efficacy in immune renal disease. The principal omega-3 polyunsaturated fatty acids are eicosapentaenoic acid and docosahexaenoic acid. They are derived from α-linolenic acid, which is found mainly in marine lipids. Eicosapentaenoic acid and docosahexaenoic acid undergo biologic transformation into trienoic eicosanoids that alter inflammatory mediators and vascular reactivity, both of which are important in the pathogenesis of certain glomerular immune diseases. Investigators have shown that proteinuria was prevented and survival was prolonged in autoimmune models of nephritis after dietary supplementation with fish oil. Furthermore, vascular damage may be modified by the influence of eicosapentaenoic acid and docosahexaenoic acid on blood rheology, aggregation of platelets, and plasma lipids. In short-term clinical studies, omega-3 polyunsaturated fatty acids seem to diminish cyclosporine-induced nephrotoxicity and the attendant complication of hypertension, to inhibit inflammatory and atherogenic mechanisms in lupus nephritis, and to preserve renal function and reduce proteinuria in IgA nephropathy. Long-term clinical trials for testing fish oil in these three clinical conditions are under way to confirm or refute these apparent beneficial therapeutic results.