Deproteinized and defatted bone pulp was preliminary calcined at NOT and then at 650-950 degrees C for 2 h in a chamber kiln under air to produce hydroxyapatite. The product contained P (about 17.5% by weight) and Ca (39.5-41.7% by weight). The crystallinity degree and P and Ca contents increased with increasing the calcination temp. The Ca/P ratio in the product was not stoichiometric.