An investigation has been made on the abnormal grain growth of crystal oriented hydroxyapatite in sintering using a high magnetic field. According to X-ray diffraction and microstructure analysis, a high magnetic field in sintering could not affect the crystal direction of the hydroxyapatite, which was previously oriented by a high magnetic field in a slip casting, but influence the growth of hydroxyapatite grains. If the magnetic field, the direction of which was perpendicular to the a- and b-axis crystal orientation of the hydroxyapatite, was applied during the sintering process, abnormal growth grains were produced. On the other hand, if the applied magnetic was parallel to the a- and b-axis crystal orientation of the hydroxyapatite, the abnormal growth was restrained and grains with rather uniform sizes were produced. (c) 2009 Elsevier B.V. All rights reserved.