To study the method and the optimal quantity of osteoblast transplantation to stimulate bone regeneration by transplanting 6～8 day old cultured osteoblasts and bFGF, together with osteoblast free calvaria of fetal rabbits into the defects of the rabbit radius. The fibroblasts were embedded in the type Ⅰcollagen in the concentrations of 10 7 ,10 6 ,10 5 , 10 4 /ml. Bone repair was evaluated by X ray, bone density,and scanning electron microscopy. Bone union ratio of the radius with transplantation of 10 7 ,10 6 ,10 5 , 10 4 /ml osteoblasts was 40%, 65%, 31 25%, 5 55% respectively at 4 weeks after transplantation, and 41 67%, 75%, 37 5%, 10% respectively at 8 weeks after transplantation. Bone density of radius defect with transplantation of 10 7 , 10 6 , 10 5 , 10 4 /ml osteoblasts was (0 112?0 018), (0 159?0 033), (0 122?0 039), (0 066?0 002) respectively at 6 weeks after transplantation and (0 150?0 059), (0 173?0 041), (0 145?0 023), (0 103?0 023) respectively at 8 weeks after transplantation, In 10 cases of bone non union, union was achieved by transplanting fetal osteoblast and basic fibroblast growth factor. This finding indicated that that transplantation of fetal osteoblasts could stimulate bone defect repair. The optimal concentration of osteoblasts implant was 10 6 cells /ml. It might be used in the treatment of bone non union.