Low-sulfur S-carboxymethyl kerateine (SCMKA) contains a fraction having higher molecular weights than 105 as revealed by gel filtration in 8M urea solution, and this fraction has been considered as an aggregate of one of the major components of SCMKA, Component 7. The high-molecular-weight fraction was successfully isolated from SCMKA into two subtractions on a preparative scale by use of Sepharose CL-6B gels. Two major components of SCMKA, i. e., Component 7 and 8, were prepared by fractional precipitation method. It was found that the amino acid compositions of the high-molecular-weight fractions were almost identified with that for Component 7, and further that their molecular weights were 12×104 and 18×104. However, a series of experiments showed that any aggregate of Component 7 and 8 or each one of them alone could not be formed in 8M urea solution at pH 7.4. In connection with the multimerization of Component 7, intermolecular crosslinkages due to cystine and lanthionine residues were examined in different manner. It is pointed out that the presence of lanthionine residues in the high-molecular-weight fraction might be most closely related to this problem.