In this study, the influences of process parameters and different cross-sectional dimensions on the tensile strength of specimens with and without a weld line are investigated. In addition, the weld line characteristics of structures with different cross-sections are explored as well. With the Taguchi method and confirmation test, it can be concluded that Taguchi method is suitable to improve the mechanical properties occurring in the injection molded UHMWPE parts. The single-factor experimental results indicate that the process parametric influence is relatively smaller than the cross-sectional dimensions on the tensile strength of specimens without weld line. The experimental observations present that the frictional heating can be enhanced the molecular bonding and self-diffusion in the frozen layer of two sides on the weld line region. The SEM images showed that the micro-voids, cracks and incomplete molecular bonding are the major surface defects on the weld line region. (C) 2009 Published by Elsevier Ltd.