Celecoxib (C), a COX-2 enzyme inhibitor, was administered at a 0.1% dose level in the diet of female Swiss Webster CFW outbred mice for life. The mice also received 1,2-dimethylhydrazine dihydrochloride (1,2-DMH) as 10 weekly subcutaneous injections at 20 microg/g body weight. The number of animals with large intestinal cancer and the total number of these cancers were 30 and 321 in the 1,2-DMH-treated group, while the corresponding figures in the C and 1,2-DMH-treated group were 29 and 156. This difference is statistically highly significant. The literature contains a limited number of publications concerning the cancer chemopreventive activity of C, particularly in mice. The present work, thus, provides additional proof in this field of interest.