Nanocrystalline hydroxyapatite [HA, Ca-10(PO4)(6)(OH)(2)] powders were synthesized by the mechanochemical-hydrothermal method using emulsion systerris consisting of aqueous phase, petroleum ether (PE) as the oil phase and biodegradable Tomadol 23-6.5 as the nonionic surfactant. (NH4)(2)HPO4 and Ca(NO3)(2) or Ca(OH)(2) were used as the phosphorus and calcium sources, respectively. The calcium source and emulsion composition had significant effects on the stoichiometry, crystallinity, thermal stability, particle size and morphology of final products. Disperse HA crystals with a 160 nm length and aspect ratio of ca. 6 were formed in an emulsion system containing 10 wt% PE, 60wt% water and 30 wt% surfactant. The HA particles had needle morphology with a specific surface area of 190 m(2)/g. With this technique, HA nanopowders with specific surface areas in the range of 72-231 m(2)/g were produced. (C) 2004 Elsevier B.V. All rights reserved.