In this study, corn fractions obtained from an isolation process of anti-mutagenic factors in our previous research work (Burgos-Hernández et al., 2001), were subjected to several analyses for chemical/structural elucidation. The anti-mutagenic activity of these fractions was tested against aflatoxin B(1) (AFB(1)) and 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), a mutagen that does not require bioactivation. Two concentrations of this agent in the corn fractions were tested for anti-mutagenicity in the Salmonella/microsomal mutagenicity assay, using tester strain TA100 with no metabolic activation. Corn fractions tested showed evidence of anti-mutagenic activity by producing a dose-response type of relationship between a constant amount of MNNG and several concentrations of tested corn fraction. Five different varieties of yellow corn were tested in order to determine if the anti-mutagenic factors were intrinsic to corn. Variety of the corn did not show an effect on the reduction of the mutagenic potential of AFB(1) suggesting that anti-mutagenic compounds are intrinsic to corn. Four corn fractions, previously obtained after the isolation process were analyzed by MALDI-MS and GC-MS. MALDI-MS showed the presence of two groups of molecules or molecular fragments. The molecular mass of one group ranged from 250 to 370 m/z, the other ranged from 540 to 640 m/z. GC-MS identified linoleic acid as one of the compounds responsible for the anti-mutagenic activity present in corn.