—The occurrencc of water soluble lipoprotein in the 105,000 g supernatant of rat brain homogenate has been demonstrated.

The lipoproteins of brain differed from those of the serum with respect to lipid composition, density and reaction to serum lipoprotein antibodies.

Acrylamide gel electrophoresis resolved the brain supernatant into four zones which stained with lipid dye. It was possible to demonstrate that these zones also contained protein by double staining of the gel for lipid and protein. Two of the zones differed in their mobility from serum lipoprotein.

Preparative acrylamide gel electrophoresis isolated protein fractions in supematant which contained both lipid and protein and permitted preliminary identification of the lipoprotein bands amongst all the protein bands resolved by acrylamide gel electrophoresis.