Apatite crystallization in the apatite-wollastonite glass exhibits a three-dimensional bulk mechanism with an Avrami parameter (n) approximate to 3, while that of the second phase (wollastonite) shows a two-dimensional surface mechanism (planar growth) with n approximate to 2. A strong effect of glass particle size on the wollastonite crystallization temperature is observed. The peak temperature is lower when the particle size is smaller.