This study investigated the efficacy of using CO2 laser irradiation to treat the surface of the magnesia partially stabilised zirconia (MgO-PSZ) in order to enhance the biocompatibility by improved wettability characteristic and bioactivity by inducing functional OH groups. The value of such an investigation would be to elucidate the mechanism of the formation of OH groups on the ceramics in the laser processing and the effects of the OH groups on the wettability characteristics of bioceramic, thereby providing a flexible and highly controllable technique to control the bioactivity and biocompatibility. Some hydroxyl groups were found on the MgO-PSZ following CO2 laser treatment at certain power densities, and the fundamental mechanism of hydroxyl group formation in CO2 laser treatment process was discussed. The surface melting on the MgO-PSZ induced by CO2 laser processing provides the Zr4+ ion and OH- ion; in turn, the corporation of Zr4+ ion and OH- ion creates the Zr-OH group on the surface. For the first time, this present work investigated the utilisation of a CO2 laser to produce the OH groups on the MgO-PSZ and discussed the correlation between the OH group and the wettability characteristics of the MgO-PSZ. (C) 2004 Elsevier B.V. All rights reserved.