Sclerostin (SOST), a member of the cystine-knot superfamily, is essential for proper skeletogenesis since loss of function mutation in SOST gene results in sclerosteosis featured with massive bone growth in humans. To understand the function of SOST in developmental skeletal tissue formation, we examined SOST gene expression in embryonic osteogenesis in vitro and in vivo. During osteoblastic differentiation in primary calvarial cells, the levels of SOST expression were increased along with those of alkaline phosphatase activity and nodule formation. In situ hybridization study revealed that SOST mRNA expression was observed in the digits in E13 limb buds and SOST expression was observed in osteogenic front in embryonic 16.5 day postcoitum (E16.5) embryonic calvariae and this expression persisted in the peripheral area of cranial bone in the later developmental stage (E18.5). These temporal and spacial expression patterns in vivo and in vitro were in parallel to those of osterix (Osx), which is a critical transcriptional factor for bone formation. Similar co-expression of SOST and Osx mRNA was observed when the primary osteoblastic calvarial cells were cultured in the presence of BMP2 in vitro. Moreover, endogenous expression of SOST and Osx mRNA was inhibited by infection of noggin-expression adenovirus into the primary osteoblastic calvarial cells, suggesting that endogenous BMPs are required for these cells to express SOST and Osx mRNA. Thus, expression and regulation of SOST under the control of BMP were closely associated with those of Osx in vivo and in vitro.