Acute renal failure is common in kidney transplantation due to immunologic, nephrotoxic, and ischemic events. In this paper the subject of posttransplant acute renal failure is reviewed in relation to arachidonic acid metabolism. Although experimental abnormalities noted in ischemia, rejection, and cyclosporin nephrotoxicity are discussed separately, it is obvious that in the clinical situation there is great overlap. The effects of altering the substrate arachidonic acid by feeding of dietary omega-3 fatty acids, both experimentally and clinically, are discussed. Finally, the limited clinical trials of prostaglandin analogues in renal transplant patients show conflicting conclusions as regards beneficial effects on rejection and renal function. Careful clinical studies of compounds with proven efficacy in animals are needed if acute renal failure posttransplant is to be modified or prevented.