Sreekumar and Hosono (42) reported that polysaccharides produced by Bifidobacterium longum revealed high levels of antimutagenicity. Kefir differs from other milk products, in that it is fermented with a mixed microflora confined to a matrix of discrete kefir grains. Within the kefir grains, lactic acid bacteria and yeasts are embedded in a slimy polysaccharide matrix, called kefiran, which is the result of the microbial metabolism of milk lactose (17, 18). The composition of the polysaccharide deriving from soymilk-kefir grains is different from that of the polysac- charide deriving from milk-kefir grains (23). To the best of our knowledge, information specific to the antimutagenic properties of kefiran is lacking, however. Further investigation is required to verify the antimutagenic properties of kefiran and the effect of polysaccharide composition upon the antimutagenic properties of kefiran.