PURPOSE: The purpose of this study was to evaluate the effect of Platelet-Rich Plasma (PRP) on the healing of the allograft for the treatment of the segmental bone defect of the ulna in Rabbits. MATERIALS AND METHODS: About 2 cm-sized segmental bone defects were created on both ulna of twenty rabbits. The rabbits were divided into two groups, even and odd number group after numbering them from 1 to 20. The segmental bone from the odd numbered animal was transplanted to the even numbered animal, and the even numbered to the odd numbered. The left side of the ulna of the animal is grafted with a segmental allograft only. The right side of the ulna was grafted with a segmental allograft and 0.7 cc of PRP. Radiographs obtained at 0, 4, 8, and 12 weeks postoperatively were graded for radiologic union. RESULTS: The use of the combination of PRP and segmental allograft demonstrated improved healing on radiolographic study compared with that demonstrated after use of allogrft alone. CONCLUSION: The results of the study suggests that the use of the combination of PRP and segmental allograft can be considered as an alternative method to manage the segmental defect of the long bone.