The experimental conditions for the synthesis of sub-micrometre, spherical particles of calcium hydroxyapatite [Ca,,(PO,),(OH),] (HA) and tricalcium phosphate [Ca,(PO,),] (TCP) are investigated through chemical coprecipitation from the aqueous solutions of calcium nitrate and di-ammonium hydrogen phosphate salts. The precipitation process employed was also found to be suitable for the production of sub-micrometre HA/TCP composite powders in situ. The synthesized pure HA and TCP powders were found to be stable even at 1300 degrees C in air for prolonged heating times. Bioceramic sample characterization was achieved by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and density and surface area measurements. Crystallographic analyses of HA powders were performed by the Rietveld method on the powder XRD data.