Oxidative decomposition of volatile organic compounds, i.e. toluene, on hydroxyapatite (HAp) under high temperatures was studied. Gaseous toluene, ethyl acetate and iso-propanol, decomposed oxidatively and converted to CO and CO2 effectively at 400-500 degrees C over stoichiometric or calcium-deficient HAp. From the direct measurement of ESR spectra under high temperatures, the ESR signals (g-value at around 2.003) for stoichiometric and calcium-deficient HAp under 300-400 degrees C were assigned to the electron trapped on vacancy in HAp. Then, it was concluded that volatile organic compounds were decomposed by the active oxygen radical due to the electron trapped on vacancy in HAp under high temperatures. We propose that HAp has also thermally-excited activity similar to TiO2. (C) 2012 Elsevier B. V. All rights reserved.