Hydroxyapatite derived from human teeth was sintered at 1200°C for 2 h. Dissolving behavior of the biologically derived HA (BHA) in distilled water was investigated and compared with an artificial hydroxyapatite (HA) made of synthetic HA powder. All disks were immersed in 40 ml of pH 7.4 distilled water (buffered using 0.05 M Tris.) for 7 and 14 days at 37°C. All detectable peaks in the HA are identical only to HA lattice planes, whereas BHA consisted of a mixture of HA and β-tricalcium phosphate (TCP). In the case of the HA specimen, the surface dissolution was initiated at grain boundaries followed by generated many separated grains and large defect like cavities. On the other hand, biologically derived HA showed that definite grains considered as β-TCP was predominantly dissolved and the grains were separated from the matrix leaving pores. In the mean time, the rest region, mainly consisting of HA, did not show any evidence of dissolution. It seems that BHA is more stable than the artificial HA in liquid environment.