Seventeen forelimbs were transplanted orthotopically from young Dutch rabbits to young New Zealand rabbits treated with cyclosporine. The transplanted limbs demonstrated significant bone growth. The growth in the transplanted limbs was about 75 to 80% of that observed in the unoperated limb. The long bones of the 3 longest surviving rabbits (133 days, 150 days, 150 days) studied radiographically demonstrated increases in length over their original lengths (humerus 22%, ulna 26%, and radius 31%). Hair and nail growth were noted at about day 10. Response to pain stimuli (withdrawal of forelimb) and functional use (ambulation with 50% weight bearing) was seen at two to three months. Permanent survival was not achieved because of a species-specific toxic wasting syndrome from cyclosporine.