Fine composite powders of yttria (3 mol%) stabilized zirconia (Z, 10 wt%) and hydroxyapatite (HA), denoted as HAZ, were prepared by the co-precipitation method. The resulting powders were characterized by XRF, TEM, EDS, XRD, FTIR, TG-DTA, and BET surface area techniques. AES and FTIR were employed to determine the surface properties of the HAZ suspensions in the presence of NH(4)PAA as a dispersant, which confirmed that the surfaces of both HA and Z were affected by the adsorbed polymers. The mechanism of NH(4)PAA adsorption on the particles was discussed. Zeta potential measurements showed that the addition of NH(4)PAA resulted in a dramatic increase in the absolute value of zeta potential. NH(4)PAA considerably enhanced the stability of the HAZ suspension via electrosteric barrier mechanisms. TEM micrographs confirmed that particles were well dispersed in the suspension. The adsorption density of the dispersant was found to decrease with an increase in pH value. (C) 2003 Elsevier Science (USA). All rights reserved.