α-Tricalcium phosphate is an important ingredient of calcium phosphate bone cements, which are used for bone defect augmentation and repair. In this study sub-micrometre sized α-tricalcium phosphate particles were synthesized by heat treating amorphous calcium phosphate. Size of synthesized particles depended on the duration and temperature of heat treatment. Longer duration and higher temperatures produced larger particles. The reactivity of synthesized particles did not correlate with the particle size – the smallest particles did not have the highest reactivity. The most reactive particles were prepared at 700-800 °C. The prepared particles were more reactive than those of conventionally synthesized α-tricalcium phosphate.