The aim of this study is to characterize the physical and mechanical properties of HDPE-alumina-HAp composites prepared by injection molding techniques and to demonstrate their superiority over unreinforced HDPE. Composites with up to 30 vol. % of filler, composed of equal volumes of HAp and alumina, were successfully processed by injection molding. On the basis of the analysis of processing results, i.e., melt viscosity, volume flow rate, shear rate, mixing torque, the critical ceramic loading was determined. Tensile tests done at varying crosshead speeds confirm that an increase in ceramic loading results in an increase in strength, as well as a simultaneous decrease in the total elongation at failure. A maximum strength of 20 MPa and a maximum tensile modulus of around 1 GPa was achieved with 30 vol % ceramic loading in semicrystalline HDPE matrix. SEVNB test results demonstrate an improvement in toughness at 20 vol %. The fracture properties are discussed in terms of interfacial bonding between ceramic fillers and the semicrystalline HDPE matrix. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2500-2511, 2011