The purpose of this study was to assess the effect of basic-fibroblast growth factor (bFGF) on the xenograft for radial bone defect in adult rats. Twenty adult Wistar rats weighing between 200 and 250g were divided into two groups; bFGF group (10 rats, 20 radiuses) and non-bFGF group (10 rats, 20 radiuses). A segmental bone defect measuring 5mm in length was made at both radiuses 10mm proximal to the wrist joint. The defect was filled with xenograft (Lubboc) measuring 3x3x5 mm in size. The xenograft was treated with 400 ng/ml bFGF (recombinant human basic-fibroblast growth factor ) mixed with liquid collagen (Vitrogen 100) in the bFGF group, but with collagen alone in the non- bFGF group. At 6 and 12 weeks after the treatment, the radiuses were harvested and examined histologically and the area of the remained xenograft not replaced by host bone was measured by image analysis system (VIDAS) on mid-sagittal section. The new bone formation and maturation from the differentiation of osteoblast was more remarkable in the bFGF group than in the non-bFGF group. At the time of 6 and 12 weeks after the treatment, the mean of the remained xenograft area was significantly smaller in the bFGF (9.16±0.49mm2, 6.20±0.30mm2) than in the non-bFGF group (12.16±0.59mm2, 10.07±0.48mm2) (P<0.001). In comparison with the areas of new bone replacemet area between 6 week and 12 week groups, sigificant and remarkable new bone replacement area could be achieved in the bFGF group than in the non-bFGF group (P<0.05). From these results, it is suggested that bFGF might increase the replacement of xenograft by new host bone and accelerate the healing process for the segmental bone defect of the radius in adult rats.