Vimentin is an important cytoskeleton protein for the biological function of macrophages. Alterations of vimentin filaments of CP-activated macrophages stained with FITC-labeled anti-vimentin antibody were observed under immunofluorescence microscope. Activated macrophages showed changes with the following characteristics: the intensity of immunofluorescence of vimentin was increased; the filaments of vimentin became thicker than those of normal macrophages when they were treated with colchicine; and the arrangement of vimentin filaments was parallel in direction to the polarization of the activated macrophages.