Copper loaded hydroxyapatite catalysts were prepared by ion exchange in aqueous phase. The copper ion exchange capacity of hydroxyapatite host structure is highly dependent on the initial copper concentration of the solution. For the lowest concentration, a pH variation of the exchange solution is observed. This change in pH may allow the deposition of a small amount of copper hydroxide at the expense of cationic substitution of copper. The increase in copper content exchanged has no effect on the profile of conversion of NO by NH3. From this, it is assumed that the copper cations substituted for calcium are not active in the reaction. The profiles of NO conversion obtained, are in agreement with the presence of a small amount of copper oxide clusters deposited on the surfaces of the apatite. (C) 2011 Elsevier B.V. All rights reserved.