Some ceramics show bone-bonding ability, i.e. bioactivity. Apatite formation on ceramics is an essential condition to bring about direct bonding to living bone when implanted into bony defects. A controlled surface reaction of the ceramic is an important factor governing the bioactivity and biodegradation of the implanted ceramic. Among bioactive ceramics, glass-ceramic A-W containing apatite and wollastonite shows high bioactivity, as well as high mechanical strength. In this study, glass-ceramics containing zinc oxide were prepared by modification of the composition of the glass-ceramic A-W. Zinc oxide was selected to control the reactivity of the glass-ceramics since zinc is a trace element that shows stimulatory effects on bone formation. Glass-ceramics were prepared by heat treatment of glasses with the general composition: xZnOx(57.0-x)CaOx35.4SiO(2)x7.2P(2)O(5)x0.4CaF(2) (where x=0-14.2mol.%). Addition of ZnO increased the chemical durability of the glass-ceramics, resulting in a decrease in the rate of apatite formation in a simulated body fluid. On the other hand, the release of zinc from the glass-ceramics increased with increasing ZnO content. Addition of ZnO may provide bioactive CaO-SiO(2)-P(2)O(5)-CaF(2) glass-ceramics with the capacity for appropriate biodegradation, as well as enhancement of bone formation.