The Chenopodium mosaic virus was purified by means of alternated low and high speed centrifugations combined with chloroform N-amyl alcohol treatment. Such preparations have a high activity, give positive tests for protein and its ultra-violet absorption spectrum is that of a nucleoprotein solution. They do not show the phenomenon of anisotropy of flow. When examined in the electron microscope they showed to be constituted of "spherical" particles of uniform size having an approximate diameter of 30 mμ.. If a pellet of the purified virus is resuspended in a small volume of 0,2 saturated (NH4)2 SO4 solution and kept at 4°C for several hours, masses of roughly rhombic crystals are formed. As far as the size of particles and the form of crystals are concerned, the Chenopodium mosaic virus resembles the southern bean mosaic virus. They differ, however, in their host range and are not related serologically.