In the present study hydroxyapatite (HA) and HA/nanosilica (NS) slurries were separately prepared by adding precipitated HA to distilled water and to colloidal silica suspension, respectively and their rheological properties were compared to each other. Both slurries where then dried, powdered, compacted as disks and sintered at 1 100–1 300°C to evaluate and compare their physical, mechanical and some biological properties. The results showed that the HA/NS slurry was more stable and thixotropic than the pure HA slurry. X-ray diffraction analysis showed that the sintered HA/NS was a multi-phase material composed of apatite, tricalcium phosphate, cristobalite and amorphous glass, depending on sintering temperature. Both mechanical and biological properties of the composite were considerably better than those of sintered HA. Bioactivity of the composite was confirmed by precipitation of apatite nanocrystals onto the surfaces of the sample after soaking in simulated body fluid. The results of cell culture tests showed the same proliferation rate of rat calvaria osteoblasts on both sintered HA and composite with higher alkaline phosphatase activity for the latter. The results indicated that the composite with improved mechanical and biological properties may act more successfully than HA as a bone scaffold material.