1. There is no evidence from these experiments that any of the bone elements of an autogenous transplant live or retain osteogenetic powers. 2. The authors have demonstrated that, with the inlay type of graft, the fixation and replacement of the graft was totally a function of the host tissue. 3. The fixation and replacement of both autogenous and homogenous bone grafts was accomplished in an identical fashion by appositional growth of the host bone. Socalled creeping substitution was but a localized phase in the process of appositional bone growth. 4. Autogenous bone grafts were superior to homogenous bone grafts experimentally only in that the early phase of healing was slightly more rapid and uniform. However, this was not due to viability and regrowth of autogenous grafts; rather it probably represented less host reaction and tissue specificity, which are factors not understood at present. 5. At the end of ten weeks, no microscopic difference could be seen between the autogenous and homogenous grafts; practically complete replacement was present in both. 6. Merthiolate-preserved bone and frozen homogenouts bone were indistinguishable experimentally. Boiled homogenous bone, however, proceeded to union much more slowly. 7. The clinical use of homogenous bone grafts is justifiable.