This study was aimed at the investigation of the thermal stability of Mg-substituted carbonated apatites over the wide temperature range. Two different apatites were studied, which were prepared by either precipitation from aqueous solution or by solid-liquid interaction. The following methods were employed: FTIR spectroscopy of the condensed gas phase to evaluate the CO and CO2 release with increasing temperature, FTIR of the solid residue after heating, XRD analysis, thermogravimetry and scanning electron microscopy. Decomposition behavior was shown to depend significantly on the synthesis method. Wet-synthesized powders are significantly less thermally stable compared with those prepared by solid-liquid interaction. Intensive release of carbon oxides from the former was observed at 300 degrees C, whereas the latter powder was relatively stable up to temperature about 1000 degrees C. (c) 2005 Elsevier Ltd. All rights reserved.