A method for manufacturing 2-hydroxy-4-(methylthio)butyric acid (HMTBA) from 2-hydroxy-4-methylthio-butyronitrile (HMTBN), where HMTBN is hydrolyzed into HMTBA in the presence of a mineral acid in an aqueous medium, the medium is neutralized by addition of a base, a first phase including at least HMTBA and salts and a second phase containing salts are separated, the method including the separation of the HMTBA from the salts of the first phase, by subjecting the latter to a chromatography.