Bone morphogenetic proteins (BMPs) are biologically active molecules capable of inducing new bone formation and are expected to be used clinically in combination with biomaterials such as bone-graft substitutes to promote bone repair. The carrier materials for BMPs have to not only secure the BMPs in the local area and diffuse them afterwards, but also to provide scaffolding for the newly formed bone. Since synthetic, biodegradable polymers with optimal properties are considered most desirable, we synthesized polylactic acid and its derivatives. Some of these were found to consistently induce ectopic bone formation when combined with BMP and implanted into the muscles of experimental animals. It was also found that the three-dimensional configuration of BMP-induced bone mass could be controlled. This means that our attempt to construct synthetic biomaterials which can induce controllable bone formation was successful.