Postischaemic reperfusion injury is often attributed to the generation of oxygenated free radicals which may subsequently promote lipid peroxidation in cell membranes. Electron paramagnetic resonance spectroscopy in association with the spin trap molecule alpha-phenyl-N-tert-butyl-nitrone allowed direct confirmation of lipid free radical production after renal ischaemia-reperfusion in an in vivo rabbit model. A 60-min period of ischaemia followed by reperfusion caused free radical production twofold greater than after 15 min of ischaemia. Glutathione and alpha-tocopherol have been measured in renal tissue, as indirect markers of lipid peroxidation. After 15 min of ischaemia followed by 10 min of reperfusion, the mean(s.e.m.) glutathione content of the ischaemic kidney was slightly but significantly reduced by 11.9(2.5)% (P < 0.003). The content of alpha-tocopherol was unchanged. However, 10 min of reperfusion following 60 min of ischaemia led to significant decrease in mean(s.e.m.) content of both glutathione (30.4(3.7)%) (2.23(0.2) versus 3.14(0.18) mumol/g wet tissue, P < 0.001) and alpha-tocopherol (46.1(7.8)%) (0.57(0.10) versus 1.09(0.14) micrograms/g wet tissue, P < 0.001) when compared to the control kidney. Under these experimental conditions, desferrioxamine (15 mg/kg administered intravenously before inducing ischaemia), a drug known to limit free radical production, significantly limited the decrease of alpha-tocopherol to 20.8(6.4)% (0.83(0.08) versus 1.05(0.04) micrograms/g wet tissue, P < 0.05), but did not prevent glutathione consumption in the reperfused kidney.