Spectroscopic properties of fluoridated CO3-apatites were studied by means of infrared (IR) absorption analysis. The peak of the IR band caused by CO32-ions at 875 cm-1 shifted to a lower frequency with the degree of fluoridation. This result suggests that there is a significant interaction between F and CO32-ions in the apatite crystals. The interaction of both these ions is discussed with regard to the solubility behavior of fluoridated CO3- apatites in the acetate buffer solution at pH 4.0 and at 37 degrees C. Solubility of these fluoridated CO3-apatites approached that of fluoridated hydroxyapatites at high fluoride content.