We analyzed the protective effect of garlic oil on hepatic and blood lipid peroxidation and the antioxidant status during buccal pouch carcinogenesis induced by 7,12-dimethylbenz[a]anthracene (DMBA) in male Syrian hamsters. Enhanced lipid peroxidation in the liver and blood of tumor-bearing animals was accompanied by a significant decrease in antioxidant levels. Topical application of garlic oil effectively suppressed oral carcinomas, decreased lipid peroxidation, and enhanced antioxidant levels. Our results suggest that garlic oil may exert its chemopreventive effects by modulating lipid peroxidation and enhancing antioxidant status in the liver and blood.