The possibility of using the antisera raised in rabbits against the porcine 25 kDa amelogenin, 32 and 89 kDa enamelins, and the 13-17 kDa nonamelogenin for the differentiation and identification of the protein components in bovine immature enamel was examined. Although the immunoreactivities of these antisera against bovine enamel proteins were weaker than those against the porcine proteins, it was found that these antisera could differentiate and demonstrate immunohistochemically a characteristic distribution of three different kinds of enamel protein components in the bovine secretory stage enamel similar to those observed in the porcine immature enamel. Of the several high molecular weight proteins being reactive to the anti-porcine 32 and 89 kDa enamelin sera, the 130 kDa protein, having the highest molecular weight, was extracted and purified from the bovine enamel sample which was obtained by peeling approximately 30-microns thickness of the outermost layer of the secretory stage enamel. The amino acid composition of the 130 kDa protein was similar to the known bovine enamelins, and was rich in aspartic acid, glutamic acid, proline, and glycine. The results could suggest that the enamelins of lower molecular weight than this protein, which are found in the bovine secretory stage enamel, are derived from this precursor protein.