Solid-state C-13- and H-1-NMR spectra of bulk high-density polyethylene samples, cylindrical in form, to which stress impacts were applied with a home-made stress-impact apparatus, were measured. The fraction of the noncrystalline component increases with an increase in the stress-impact strength. In the crystalline region, the monoclinic crystalline component appear with the stress impact, in addition to the major orthorhombic crystalline component. Furthermore, dynamic characterization was carried out on the basis of the observed values of the relaxation parameters H-1 T-2 and T-CH of the H-1 and C-13 nuclei.