Influence of postmortem time and temperature on osteoinductive activity of demineralized microperforated ethylene oxide-sterilized syngeneic bone implant in the rat. Bone morphogenetic protein is labile and easily inactivated by many extracorporeal factors. It is crucial to establish whether delay in retrieval of donor bone and ambient holding temperature of the donor body influence osteoinductivity of bone left in situ. Of ten adult rats that were killed, five were kept at 4 degrees and five at room temperature. Femurs were harvested at 24, 36, 48, 72, and 168 hours. After processing, segments were implanted in 20 four-week-old syngeneic rats for 14 days. The level of osteoinduction was evaluated histologically. It was excellent in the 4 degrees group in the 24-, 36-, and 48-hour specimens but less advanced at 72 hours. Bone taken from the room temperature group showed findings identical to those kept at 4 degrees through 36 hours, but osteoinduction was less advanced at 48 hours and absent at 72 hours. No bone formed at 168 hours in either temperature group. The following observations were made. (1) Osteoinductivity of demineralized bone left in situ after death was unexpectedly stable. (2) Retrieval time was extended by donor cooling. (3) Microperforated demineralized bone actively induced new bone formation. (4) Ethylene oxide does not inhibit osteoinduction when correctly applied for sterilization. If confirmed in humans, retrieval of bone to be used for osteoinduction could be delayed for some hours, particularly if the donor was immediately refrigerated. This would increase the effective number of bone tissue donors and utilize an undeveloped resource. 