Bi-phasic calcium phosphate (BCP) bioceramics containing hydroxyapatite (HA) and tri-calcium phosphate (TCP) phases have recently attracted attention as an ideal bone graft substitute due to their controlled resorption in the body fluid upon implantation. In this study, the HA and BCP phases were prepared by in situ method, using natural goniopora under microwave irradiation. Fourier-transform infrared (FT-IR) and powder X-ray diffraction (XRD) methods were employed to investigate proof of HA and BCP formations. XRD results show that the major characteristic peaks of HA appear in the regions of approximately 26°, 28°, 29°, 30-35°, 39°, 46°, 49° and 50° (2θ). FT-IR results indicate that there are no occurrences of impurities during HA and BCP formations. Reinforcement of zirconia in the in situ formation of HA leads to a more resorbable phase of β-TCP since the influence of zirconia induces faster decomposition of HA, as indicated by differential thermal (DT) analysis. The in vitro physiological stability of prepared materials was performed in phosphate-buffered saline (PBS) of pH 7.4 at 37 °C in a thermostatic water bath, and the results indicate that the resorbable nature of BCP lies in between the resorption levels of HA and TCP. Solubility of the BCP can be controlled by the addition of zirconia corresponding to clinical applications. © 2003 Elsevier B.V. All rights reserved.