The changes in the protein composition of wool following suppression of wool growth by mimosine and cyclophosphamide have been examined. Polyacrylamide gel electrophoresis of high-sulfur and low-sulfur protein fractions isolated from wool growth before and after a chemical defleecing treatment showed that the same protein components were present but in different proportions, and that even after three months the protein composition have not reverted to pretreatment composition. These variations in protein compistion along the wool fiber could be important as they may alter the physicochemical and textile processing properties of wool grown after chemical defleecing.