With respect to the e!ect of material factors on calcium phosphate biomaterial-induced osteogenesis, the osteoinductive property of two kinds of porous hydroxyapatite ceramics, which were made by di!erent producers, was investigated in dorsal muscles of dogs. One hydroxyapatite ceramic (S-HA), macroporous implants with rough pore walls containing abundant micropores, was made by Sichuan Union University (Chengdu, China); the other hydroxyapatite ceramic (J-HA), porous implants with smooth macropore walls composed of regularly aligned crystal grains, was provided by Mitsubishi Ceramic Int. (Japan). Di!erent tissue response was detected histologically and microradiographically after the ceramic samples had been implanted in dorsal muscles of dogs for 3 and 6 months. Bone formation was found in S-HA at 3 months, which increased at 6 months. In contrast, no bone formation was detected in J-HA at both 3 and 6 months. These results indicate that with the special architecture, calcium phosphate ceramic can induce bone formation in soft tissue. As both materials were very similar in their chemical and crystallographic structures, but varied in their microstructures, the latter seem to be an important factor a!ecting the osteoinductive capacity of calcium phosphate ceramics. These data suggest that, by controlling the preparation of calcium phosphate ceramic, bone substitutes with intrinsic osteoinductive property can be developed from calcium phosphates.