A method has been developed for the analysis of hexitolamino acids formed by acid-catalyzed hydrolysis of nonenzymatically glycated proteins that have been treated with sodium borohydride. The hexitolamino acids are converted into phenylthiocarbamyl (PTC) derivatives which are analyzed by reverse-phase HPLC. The PTC derivatives of N alpha-hexitolamino acids behave like lactones, migrating on the column more slowly than the corresponding PTC-amino acids. The PTC derivatives of N epsilon-glucitol- and N epsilon-mannitol-lysine are probably free acids, since they migrate faster than PTC-lysine. The method, which can be used to determine the degree of glycation of N-terminal and lysyl residues, has been applied successfully to human hemoglobin, serum albumin, and ocular lens proteins.