Abstract: The present study has investigated the chemopreventive and antilipidperoxidative potential of Annona squamosa bark extracts in DMBA induced hamster buccal pouch carcinogenesis. Oral squamous cell carcinoma was induced in hamster buccal pouches by painting with 0.5% 7,12-dimethylbenz (a) anthracene (DMBA) three times per week for 14 weeks. We observed 100% tumor formation in DMBA painted hamsters. Oral administration of aqueous and ethanolic bark extracts of Annona squamosa at a dose of 500 mg kg-1 body weight and 300 mg kg-1 body weight, respectively prevented the tumor formation as well as decreased the levels of lipid peroxidation byproducts and enhanced the antioxidants defense mechanism in DMBA painted hamsters. The effect of ethanolic bark extract is however more potent than aqueous extract of Annona squamosa barks. Our results suggest that Annona squamosa bark extracts exert their anticarcinogenic effect by modulating the status of lipid peroxidation and antioxidants in DMBA painted hamsters.