The chemotactic activity of lowdensity lipoprotein(LDL), oxidized LDL(OLDL),very LDL(VLDL) and oxidized VLDL(OVLDL)for human monocytes was examined, respectively,by micropore filter mothod using modified Boyden chamber. The results showed that LDL was chemotactic for monocytes, and its chemotactic activity increased significantly when it was modified by oxidation. However VLDL was not chemotactic,whereas OVLDL was significantly chemotactic for human blood monocytes.