The morphology of transcrystalline isotactic polypropylene under tensile stress was studied with wide-angle synchrotron X-ray diffraction. The strain was apparently generated predominantly within the amorphous phase because no change in the crystal structure or in the orientation of the lamellae was detected. The results are interpreted in terms of anchoring of the trans crystalline layer to the fiber surface, and the possible consequences of these morphological features on the mechanical properties of the aramid-polypropylene composite as a whole are discussed.