BACKGROUND Spirulina maxima (Sm) is a cyanobacterium well known because of its high nutritive value, as well as its anti-inflammatory, anti-hyperlipidemic, antioxidant, and anti-genotoxic activities. OBJECTIVE To determine the capacity of Sm to inhibit the induction of aberrant colon crypts (AC), as well as the level of lipid peroxidation and DNA oxidative damage in mice treated with azoxymethane (AOM). METHODS Sm (100, 400, and 800 mg/kg) was daily administered to animals by the oral route during 4 weeks, while AOM (10 mg/kg) was intraperitoneally injected to mice twice in weeks 2 and 3 of the assay. We also included a control group of mice orally administered with distilled water along the assay, as well as other group orally administered with the high dose of Sm. RESULTS A significant decrease in the number of AC with the three tested doses of Sm, with a mean protection of 51.6% respect to the damage induced by AOM. Also, with the three doses of the alga, we found a reduction in the level of lipoperoxidation, as well as in regard to the percentage of the DNA adduct 8-hydroxy-2'- deoxyguanosine. CONCLUSIONS Sm possesses anti-precarcinogenic potential in vivo, as well as capacity to reduce the oxidative damage induced by AOM. CONCLUSIONS Azoxymethane (AOM) induced a high number of colon aberrant crypts in mouse. It also increased the level of peroxidation and of DNA oxidation in the same organ.Spirulina maxima significantly reduced the number of AOM-induced colon aberrant crypts in mouse. It also reduced the AOM-induced lipid and DNA oxidation in mouse.The results suggest a chemopreventive potential for the tested algae.