A new approach for bone regeneration is needed for idiopathic osteonecrosis of the femoral head (ION). Core binding factor alpha1 (Cbfa1) was reported in 1997 as the most important transcription factor for osteoblastic differentiation. The transgenics of transcription factors affecting bone formation might be useful tools for the bone regeneration. The purpose of this study was to investigate the effects of the implantation of adenoviral vectors carrying Cbfa1 genes implanted with biodegradable porous materials on bone formation in an animal model of ION. Robust and rapid bone regeneration in large bone defects was achieved with the implantation of adenoviral vectors carrying Cbfa1 genes. These results suggest that the Cbfa1 genes induce a rapid osteoblastic differentiation and the biodegradable scaffold successfully functioned as a delivery vehicle for the Cbfa1 gene, as they induced osteogenic repair in vivo, even in necrotic bone.