Bone formation in vertebrates depends on the proliferation and differentiation of chondrocytes and osteoblasts, which are derived from a mesenchymal precursor cells and are required for skeletal development. This process relies on many transcription factor genes that have functions in bone cell proliferation and differentiation. Over the years, various transcription factors that play essential roles for skeletal formation have been identified in in vivo and/or in vitro molecular and genetic studies. In regulation of bone formation, signaling pathways with these factors have also been established. Major transcription factors including Sox9, Runx2, and Osterix, which are active in chondrocytes or osteoblasts or even in both cells, are indispensable for chondrocyte and/or osteoblast differentiation. Here, the transcriptional regulation of these genes for bone formation will be reviewed on the basis of in vivo mouse models.