It is now believed that free radicals and eicosanoids participate in the pathogenesis of immune mediated mesangial cell injury and renal tissue damage including glomerulonephritis. But relatively little information is available about the role of essential fatty acids, (EFAs), the precursors of eicosanoids, in renal diseases. We studied the levels of superoxide anion, hydrogen peroxide, lipid peroxides and the concentrations of various metabolites of EFAs in the plasma phospholipid fraction of patients with glomerular disorders. A significant increase in the production of superoxide anion and hydrogen peroxide both by unstimulated and phorbol-myristate acetate (PMA)-stimulated leukocytes, increase in the plasma lipid peroxide levels and a marked reduction in the levels of arachidonic acid (AA) and eicosapentaenoic acid, the precursors of 2 and 3 series prostaglandins (PGs) respectively, were observed in these patients. Since eicosapentaenoic acid and prostacyclin, which is derived from AA, are believed to be of benefit in the prevention of progression of renal disease, and as free radicals can cause renal dysfunction, our results suggest that free radicals and the metabolites of EFAs play a significant role in the pathogenesis of glomerular disorders.