[en] X-ray diffraction patterns of the α- and β-crystalline phases of natural, chemically modified, and MMA-grafted wool fibers were investigated. In the grafted fibers variation of the equatorial and meridional scattering intensity during the α-β transformation was inhibited. This indicated that the grafting had stabilized the structure to the α-β transformation. The average crystallite size was found to increase with the extent of grafting, and the degree of orientation appeared to decrease with percent graft-on. SEM studies revealed little damage to the surface topography of wool fibers after chemical treatments. Graft copolymerization with MMA made the fiber surface regular and smooth, mainly because of deposition of polymer in the escarpment, thus reducing the sharpness of the scaly structure. Scanning electron micrographs of the peeled-off surface and cross sections of the grafted fibers indicated that a significant amount of polymer was deposited in the medullae of the fibers