Organ damage caused by iron overload has been mostly attributed to iron-induced peroxidation of membrane lipids. Using the ferrocene iron-loaded rat model, we studied ethane exhalation as a direct marker of in vivo lipid peroxidation, as well as concentrations of alpha-tocopherol and ubiquinol 9/10 in liver and plasma as indirect markers of this process. The feeding of a diet enriched with 0.5% TMH-ferrocene up to 31 weeks resulted in a large increase in liver iron concentration to about 25 mg/g wet weight (w wt). At lower, predominantly hepatocellular liver siderosis, the breath ethane exhalation was dependent on dietary vitamin E (VitE) supplements (onset of ethane exhalation at liver-Fe > 2 mg/g w wt on vitE-restricted diet; > 5 mg Fe per gram on VitE-replete diet). At severe liver siderosis, breath ethane exhalation reached a maximum of approximately 8 nmol/kg/hr independent of VitE supplementation. Plasma as well as hepatic alpha-tocopherol decreased with progressive iron loading. In addition, a significant depletion in hepatic ubiquinol 9 and 10 was noted.