The modifying effects of administering an ethyl acetate extract of Kurosu (EK), a vinegar made from unpolished rice, in drinking water on the development of azoxymethane (AOM)-induced colon carcinogenesis were investigated in male F344 rats. Animals were given 2 weekly subcutaneous injections of AOM (20 mg/kg body weight). They also received drinking water containing 0%, 0.05%, or 0.1% EK for 35 wk, starting 1 wk after the last dosing of AOM. EK administration significantly inhibited the incidence and multiplicity of colon adenocarcinoma (P < 0.05), compared with those in the AOM alone group. These findings suggest that EK may be effective for inhibiting colon carcinogenesis.