The changes in microstructural parameters in hydroxypropyl methylcellulose (HPMC) polymer films irradiated with 8 MeV electron beam have been studied using wide-angle X-ray scattering (WAXS) method. The crystal imperfection parameters such as crystal size (N), lattice strain (g in %), and enthalpy (alpha*) have been determined by line profile analysis (LPA) using Fourier method of Warren. Exponential, Lognormal, and Reinhold functions for the column length distributions have been used for the determination of these parameters. The goodness of the fit and the consistency of these results suggest that the exponential distribution gives much better results, even though lognormal distribution has been widely used to estimate the similar stacking faults in metal oxide compounds. (C) 2008 Wiley Periodicals, Inc.