Many plants found in nature have been used to treat various illnesses. One such plant is oregano (Kekik in Turkish). Health beneficial effects of carvacrol obtained from oregano oil have been shown scientifically. We have investigated the comparative effects of carvacrol in the liver of rats subjected to ischemia-reperfusion defect, with silymarin. To test the effects we formed four groups using male Wistar albino rats. Group I was control. The other three groups of animals were administered 60 min prior to surgical operation single doses of physiological serum, carvacrol and silymarin, respectively. Group II, III and IV animal were subjected to 45min long liver ischemia and 60min reperfusion. Blood and tissue samples were collected for biochemical and histological analysis following the test. AST and ALT values obtained after biochemical analysis of the serums showed statistically significant difference in group II than the other three groups. A statistical evaluation of the serum AST levels among the groups II, III and IV showed that both groups III and IV which had no difference in between were significantly different in a positive way from group 11 (p < 0.00 1). As to the serum ALT levels, difference between group II and group III (p < 0.00 1) and group II and group IV (p < 0.01) was found significant. No statistical difference was observed in groups I, III and IV for GSH, MDA and CAT levels of the liver. A statistical evaluation of the GSH level in group III and group IV was found to be significantly different from group II (p < 0.001) without any difference between them. A similar evaluation for MDA and CAT levels among the revealed no difference between group III and group IV, however, group II showed difference with group II and group IV (p < 0.05). Histological findings were in harmony with the biochemical results. We conclude that carvacrol protects the liver against defects caused by ischemia and reperfusion, and carvacrol is not hepatotoxic at the applied dosage. (c) 2007 Elsevier GmbH. All rights reserved.