Objective: To study the effects of basic fibroblast growth factor(bFGF) on promoting new bone formation in repairing mandibular defects.Methods: 15 mm?6 mm bilateral mandibular periosteum bone defects were made surgically in 18 adult New Zealand rabbits, the right defects were repaired with natural non organic bone (NNB) combined with bFGF at 40 ng/mm 3, the left defects were repaired with NNB. Specimens were obtained 3, 6, 12 weeks after operation respectively. The effects were evaluated with toluidine blue stain observation, tetracycline fluorescent microscopic examination and computerized quantity analysis. Results: More chondrocytes were observed in the right defects 3 weeks after operation. 3, 6, 12 weeks after operation the new bone formation (?m 2) in the right defects was 66.092?6.379, 130.198?13.213 and 235.374?16.773 respectively; that in the left defects 21.844? 7.731 , 62.694?10.389 and 160.184?14.793 respectively( P