A self-made low-frequency vibration-assisted injection-molding (VAIM) device was adopted to explore the relationship between mechanical property and morphology for high-density polyethylene injected moldings. The main processing variables for the VAIM are vibration frequency and vibration pressure amplitude, and tensile properties and morphology were investigated under different VAIM processing conditions with conventional injection molding for comparison. The moldings prepared by VAIM exhibit a very well defined laminated morphology composed of a layered structure with enhanced crystallinity. Increased with vibration frequency at constant vibration pressure amplitude, the shish-kebab structure is exhibited in the shear layer of the specimen prepared by VAIM, whereas row nucleation lamella exists in the same layer produced by enhanced vibration pressure amplitude at a constant vibration frequency. These oriented structures and enhanced crystallinity, confirmed by scanning electron microscopy, wide-angle X-ray diffraction, and differential scanning calorimetry, serve to obtain stronger injection moldings. (C) 2004 Wiley Periodicals, Inc.