The present Study looks into the microstructural changes in C108 (Bombyx mori) silk fibers, induced by electron irradiation. The irradiation process was performed in air at room temperature by the use of 8 MeV electron accelerators at different doses: 0, 25, 50, 75, and 100 kGy, respectively. The changes in microstructural parameters in these natural polymer fibers have been studied using wide-angle X-ray scattering method. The crystal imperfection parameters such as crystallite size < N >, lattice strain (g in %), and enthalpy (alpha*) have been determined by line profile analysis using Fourier method of Warren. Exponential, lognormal, and Reinhold functions for the column length distributions have been used for the determination of these parameters. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 2183-2189, 2010