A comparison was made of the serum lipoprotein-cholesterol profile, obtained by cellulose acetate electrophoresis coupled with an enzymatic stain for total cholesterol, of the adult male rat, mouse, rabbit, dog, monkey and human. Four cholesterol-staining lipoprotein bands were detected in rat serum, while only three cholesterol-staining lipoprotein bands were present in the other species studied. The apparently unique lipoprotein-cholesterol band in the rat was found to electrophoretically migrate in the prealbumin region of rat serum, has been named prealbumin lipoprotein-cholesterol (PAL-C) and was shown to be a high density lipoprotein (HDL). Of the species studied those more susceptible to experimentally induced atherosclerosis had higher low density lipoprotein-cholesterol to HDL-cholesterol ratios compared to those species least susceptible to experimentally induced atherosclerosis.