By C-method of chromosome staining three transplantable murine tumor lines passaged in vivo were studied. Marker chromosomes were discovered in all cell lines under observation. The previously described marker chromosomes B and C were found in transplantable Ehrlich ascites carcinoma cells, acrocentric chromosome with additional C-band --in cells of line C-37, acrocentric chromosome with double quantity of subcentrometric heterochromatin in cells of line TG-180. The data obtained make it possible to distinguish the lines under study by C-method of chromosome staining.