This experimental study was undertaken in mice to investigate the procedures for storage of allogenic cancellous bone. Cancellous grafts were were stored at -80 degrees C, -196 degrees C or freeze dried. Grafts were implanted into a defect in the recipient's femur and after one week the cellular kinetic activity was analysed by autoradiography. For immunological study, the grafts were implanted into the recipient's muscle, and 2 weeks later the sensitising properties were examined by killer T-cell toxicity and the complement dependent cytotoxicity test. The capacity for osteogenesis of grafts frozen at -196 degrees C was similar to or higher than those freeze dried, but it was low when storage was at -80 degrees C. Immunogenicity was not affected by these three methods of storage and was very similar to that of fresh autografts. Antigenicity of allografts can be decreased by the freezing procedure. We suggest that the greater osteogenic potency after freezing at 196 degrees C is related to the lesser degree of degeneration of the bone matrix.