Increasing the amounts of calcium and phosphate ions released in vivo by β-tricalcium phosphate (β-TCP) may enhance its osteogenic activity for bone repair and regeneration. Planetary ball milling of β-TCP powder using acetone and 1-mm-diameter zirconia beads reduced the average particle size of the powder to ∼ 0.4 µm within 120 min and converted most of the crystals to an amorphous phase of calcium orthophosphate. Immersing the treated powder in a tris-HCl buffered solution of pH 7.4 for 24 h at 37 °C dissolved calcium and phosphate ions with several times the yield from that of the original β-TCP powder. This approach is expected to be useful for preparing composite materials with an enhanced therapeutic effect on living tissues.