Abstract: The new keratin-reducing substances useful in compositions for permanent shaping of hair are glyceryl esters of cysteine, especially the monoglyceryl esters. As monoglyceryl esters of cysteine 2-amino-3-mercaptopropionic acid-(2',3'-dihydroxypropyl)ester and 2-amino-3-mercaptopropionic acid-(1',3'-dihydroxyisopropyl)ester are particularly preferred. A preferred embodiment of the compositions for permanent shaping of hair consists of a ready-to-use mixture of a water-free component including at least one glyceryl ester of cysteine and at least one other component which is kept physically separately from the water-free component until the mixture is prepared. The compositions also can include other conventional ingredients normally used in permanent shaping compositions such as surfactants and thickeners. The compositions have a preferred pH range of 6.0 to 8.5 and contain from 8 to 28 percent by weight of the glyceryl esters of cysteine.