Bone morphogenetic protein (BMP) was combined with true bone ceramic (TBC) in an attempt to produce a bone grafting material possessing the cancellous structure, osteoconductivity, and osteoinductivity of biologic bone. To determine the osteogenetic ability of this material (BMP-TBC) within bone marrow, BMP-TBC and TBC alone were implanted in the femoral condyles of Japanese White rabbits, and histographs of these implants, taken serially, were compared. Woven bone formation was observed both at the periphery and within surface pores of the BMP-TBC implants one week after implantation; these implants thus became secured to the host bone bed at an earlier stage than did TBC alone. The amount of new bone formation increased at a significantly higher rate with BMP-TBC than with TBC alone during the first four weeks. Therefore the BMP in BMP-TBC implants acts at an early stage on BMP-responding cells entering the pores of the TBC. These data also suggest that TBC, as a carrier for BMP, provides a favorable environment for the promotion of new bone formation.