It was found that the peptides produced from bovine blood plasma proteins by enzymatic hydrolysis have antigenotoxic effects. The proteins were hydrolyzed with several proteolytic enzymes available for industrial use and the antigenotoxicity was determined by measuring the reduction of DNA damage using the Comet assay. The most efficient protease for producing the active peptides was pepsin and the peptic hydrolysate of albumin showed nearly perfect activity of preventing DNA damages. It was found that the antigenotoxic effect of peptides might be due to the protective interactions between cells and peptide molecules rather than the direct inactivation of the mutagen, MNNG by peptides. The phenyl groups of aromatic animo residues at peptide ends were supposed to contribute to antigenotoxicity because the subsequent chymotryptic hydrolysis of each hydrolysate increased the activity. By ultrafiltration and Sephadex G-25 gel chromatography, the molecular weights of active peptides were observed as below 1.000. The results of this study showed a possibility of utilizing bovine albumin as a source for chemopreventive functional peptides.