Hydroxyapatite (HA) has been of interest in many industrial applications, such as ion exchange, catalysis and biomaterials. Chelating agents have often been used to prepare inorganic powders in the form of sphere, rod, whisker and fiber. In this study, HA whiskers were synthesized directly from typically shaped HA powders by refluxing at 80 and 100 degrees C for 24h using ethylenediamine tetraacetic acid (EDTA). 3% or 6% of hydrogen peroxide (H2O2) was used to promote precipitation of HA crystals. The pH of the solution was adjusted at 7 or 9 by adding ammonia solution. The higher the H2O2 concentration, pH value and refluxing temperature, the longer and thinner whiskers were formed. The whiskers produced at 100 degrees C with 6% of H2O2 and pH 9 had the highest aspect ratio of about 50-60 (a length of 3 mu m and a width of 0.05 mu m). (C) 2007 Elsevier B.V. All rights reserved.