Abstract The present study was undertaken to determine whether hepatic ischemia and the subsequent reflow of blood had any effect on the levels of endogenous coenzyme Q homologs, α-tocopherol, and glutathione, and whether coenzyme Q 10 (6 mg/kg of body weight) altered these levels. Ischemia of the rat liver for 90 min resulted in decreases of 19.1 and 19.6% of endogenous α-tocopherol and total glutathione (GSH + GSSG) without significant changes in the levels of endogenous total coenzyme Q homologs, (oxidized and reduced). Restoration of the blood flow resulted in marked decreases in endogenous coenzyme Q homologs, α-tocopherol, and total glutathione in the control group. In coenzyme Q 10-treated animals, however, there were no changes in the levels of endogenous total coenzyme Q 9, α-tocopherol, or total glutathione as well as in the level of the enhanced total coenzyme Q 10 during the reperfusion period. On the other hand, decreases in α-tocopherol and total glutathione during the period of ischemia remained unchanged. These results are compatible with the assumption that cellular damage caused by hepatic ischemia can be explained by free radical reaction processes during ischemia and especially, reperfusion and suggest that exogenous coenzyme Q 10 functions as an antioxidant with endogenous coenzyme Q homologs, α-tocopherol, and glutathione in lipid peroxidation during reperfusion.