The effects of KSYS Compound on the frequency of SCE of marrow cells in vivo of old mice were studied in this article. the results were as follows: the frequency of SCE in marrow cells of old mice were obviously higher than those in amrrow cells of young mice; the frequency of SCE in marrow cells from old mice fed KSYS Compound were obviously lower than those from old mice without KSYS Compound. the results showed that the frequency of SCE in mouse marrow cells increase with advance of age. the KSYS Compound can impede a...