Pulp tissue, enamel and incisal and basal dentine of the mandibular incisor were taken from one litter of rats and transplanted subcutaneously or intracerebrally to sex-matched, 5-day-old animals of the subsequent litter of the same parents. As sham-operations the mere transplantation instrument was inserted into the transplantation sites. With some exceptions, the host animals were killed 4, 32, 128–138 and 210 days after the operation and the transplantation sites were examined either grossly or microscopically or both. The pulp tissue transplantation had resulted in formation of osseous tissue observed 128 days post-operatively. Bone was found in association with many of the basal dentine transplants 128–210 days after their insertion whereas no such tissue was observed with the transplanted enamel of incisal dentine. The sham-operation seemed to have elicited intracerebral bone formation in two animals. The osteoinductive activity of the transplanted tissues seemed reduced by their mineral phase. Further, in contrast to deminerahzed hard tissues, the non-demineralized inductive agents do not seem to possess bone morphogenetic propert