Cucurbitacins are a natural cell?permeable triterpenoid compound isolated from Cucurbitaceae and Cruciferae. Cucurbitacins have been used as folk medicine because of their anti?inflammatory and analgesic effects. In the present study, we investigate the anti?cancer effects of cucurbitacin I on colitis?associated colon carcinogenesis induced by azoxymethane (AOM)/dextran sodium sulfate (DSS) in BALB/c mice. Cucurbitacin I treatment attenuated loss of body weight and decreased the number of colon tumors. Western blot analysis showed that cucurbitacin I treatment significantly inhibited the protein expression of inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF)?α and interleukin (IL)?6. These results suggest that cucurbitacin I suppressed inflammatory reaction and tumor development in colitis?associated colon carcinogenesis.