Bone grafts remains the most effective grafting material because it provides the three elements required for bone regeneration: osteoconduction, osteoinduction and osteogenic cells. Bone grafts are used in the repair of significant fractures, the treatment of skeletal tumors and the reconstruction of failed total arthroplasties. Allografts of bone elicit transplantation immunity and this immunogenicity may cause the higher failure rate of these grafts. In an attempt to reduce the immunogenicity of the graft, allogenic bone has been frozen and freeze-dried. Because of increasing clinical use of bone grafts and the unacceptable failure rate, it would be advantageous to better understand the biological response to grafts in order to better define the parameters necessary for a successful bone grafts.