In the present report we determined the protective capacity of grapefruit juice (GJ) against molecular andcellular damage in azoxymethane (AOM) treated mice. Animals were daily administered GJ orally (0.8, 4.1, and8.2 μl/g) for seven weeks, as well as intraperitoneally (ip) injected with AOM twice (weeks 2 and 3 of the assay).Control groups administered with water, with the high dose of GJ, and with AOM injected in weeks 2 and 3were also included. The results showed a significant, dose-dependent protection of GJ on the number of colonaberrant crypts (AC) induced by AOM. The highest inhibitory effect was reached with the highest tested doseof GJ, decreasing ACF by 51% and 43% at weeks 4 and 7 of the assay. Regarding protein and lipid oxidationwe also found a dose-dependent decrease caused with GJ in comparison with the increased levels produced byAOM. Therefore, our results established chemopreventive potential for GJ, and suggested effects related to itsantioxidant capacity. Finally, we found that the tested agents induced neither micronuclei increase nor alterationin bone marrow cytotoxicity.