The isolation and properties of a protein obtained in crystalline form from bovine liver, kidney, and spleen are described. The protein, which appears not to have been previously described, was originally named football protein by Sumner and Dounce. Football (FTBL) protein is a tetramer having a molecular weight of about 264,000 A monomer molecular weight of about 66,000 was obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A s 20 =11.54, a rough diffusion constant of 3.68×10 −7 cm 2 /s, av=0.739, and an amino acid composition were obtained for the protein. The protein was also prepared from lamb liver in a concentrated but noncrystalline form. Anti-FTBL protein, prepared by immunizing rabbits with 2x crystallized beef liver protein, was used as a reagent to determine the tissue distribution of FTBL protein. The protein is present in beef liver, spleen, kidney, and white blood cells, but absent from beef red blood cells. An immunochemically related but not identical protein is present in rat liver, spleen, and kidney, but is not detected in rat thymus, pancreas, or heart muscle. As determined by immunodiffusion analysis, beef liver, kidney, and spleen protein and the lamb liver protein are immunologically indistinguishable from one another. Although tested on various substrates, no enzymatic activity has been found yet which can be attributed to crystalline beef FTBL protein. A list of the enzymes tested is given.