In this study, the carbonate incorporation into the hydroxyapatite (HAp) lattice under various pH conditions was investigated. Crystalline-sodium and carbonate-containing calcium HAp (NaCO(3)HAp) powders were prepared using an oxidative decomposition of calcium-EDTA chelates in a sodium phosphate solution with hydrogen peroxide. The powders obtained were characterized by X-ray diffraction, infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and elemental analysis. Depending on pH, spherical particles approximately 3.5 mu m in diameter or hexagonal prismatic particles measuring 3-9 mu m in length were obtained. Various characterization techniques showed that the precipitates were a single-phase NaCO(3)HAp. The carbonate content and the lattice parameters of the HAp were a function of solution pH. Maximum carbonate incorporated into the HAp lattice was at pH=10, corresponding to lattice parameters of a=0.93880 nm and c=0.69070 nm. Furthermore, spectroscopic analyses indicate that the as-prepared samples are B-type carbonated HAp, in which carbonate ions occupy the phosphate sites. After heat treatment at 965 degrees C, most of the carbonate is removed from the HAp lattice.