Third generation synthetic mechanical analogue models of bones manufactured by Pacific Research Laboratories. Inc. (PRL) are popular tools for use in mechanical testing of various orthopaedic implants. One problem with these models is that the current epoxyshort fiberglass composite used as the cortical bone substitute is susceptible to crack formation and failure in fatigue. The purpose of the present study was to compare fracture mechanics properties of the current baseline (established PRL "Third Generation'" E-glass-fiberepoxy) composite analogue for cortical bone to six new composite materials formulations proposed for use as a 4th generation cortical bone analogue material. Plane strain fracture toughness tests were performed on all materials; fracture toughness was significantly increased as much as 58% in the new composites as compared to the baseline. Fatigue crack propagation rate tests were performed on the baseline material and the new composite with the greatest increase in fracture toughness. The fatigue crack propagation rate was significantly decreased in the enhanced composite. These results indicate that the bone analogue models using this new analogue cortical bone material may exhibit superior performance in fracture and fatigue. Further testing of the new composite materials in bone models is required.