Abstract. Fluoride (F-)-substituted type-B carbonate-containing hydroxyapatites (CHAPs) were prepared as bone substitutes with a F-releasing ability. The F- contents in the F-substituted CHAPs were 16-22 times larger than that in normal adult human bones. The carbonate contents in the F-substituted CHAPs corresponded to that in human bones. The F-substituted CHAPs released F- in an acetic acid – sodium acetate buffer at pH 4.9; within only 3 h, the F- concentration in the buffer increased to more than 63.9 µg L-1, which was 1.5~8.9 times higher than that in a body fluid of normal adult humans. Although the F- concentration rapidly decreased probably due to the precipitation of a certain phase containing F-, the F-substituted CHAPs exhibited the ability to increase the F- concentration in a body fluid by bone resorption. Therefore, it is expected that the F-substituted CHAPs will be feasible as a F-releasing material for promoting bone formation.