Preliminary determinations of amino acid compositions of proteinaceous residues obtained from several Pleistocene fossil bones. These showed the presence of the same amino acids as could be obtained from similarly treated recent bones. Amino acid analyses were made of proteins persisting in Pleistocene bones from the Rancho La Brea tar pits and in recent desert-dried bone used as control. The total amount of protein in the fossils lies between one-sixth and one-half that in recent bone. The ratios of amino acids in the four samples are similar and point to the presence of other proteins besides the collagen the electron microscope shows to be present.