Fermented milk and lactic acid bacteria have been considered to provide potential health benefits to human beings, Milk contain casein contributed to the high desmutagencity, and fermentation by lactic acid bacteria produced various hydrolytic peptides contributed to the high desmutagenic property of fermented milk. Desmutagenic property of milk, was also depended on the strains of lactic acid bacteria and the fermentation time. Not only the proteolytic products of casein, but polysaccharides, fatty acids and the bacterial cells, all contributed to the desmutagenic properties. Lactic acid bacteria isolated from various fermented products of dairy and non-dairy origin, traditional fermented foods, animal and human feces have shown desmutagencity against the mutagenicity of known chemical mutagens and also to food-borne mutagens. Most of the studies with lactic acid bacteria showed that colon tumour can be controlled to some extend by the consumption of dairy products supplemented with lactic acid bacteria. By revealing the molecules of lactic acid bacterial cells involved in binding (as binding and antimutagencity are well correlated and the bound mutagens were inactive), can lead to the modification of cell walls of lactic acid bacteria to suit to inactivate a wide spectrum of chemical mutagens and carcinogens.