To investigate the role of matrix Gla protein (MGP), which can bind mineral ions through gamma-carboxylated glutamic acid residues, in vascular calcification, we examined the expression of MGP in an in vitro calcification model by using bovine vascular smooth muscle cells (BVSMC). The expression of MGP mRNA was decreased during BVSMC calcification and its levels were inversely correlated with the quantities of BVSMC calcification. MGP mRNA expression was restored to the level of uncalcified control by inhibiting BVSMC calcification with bisphosphonates. These data suggest that the expression of MGP gene is modulated in the development of vascular calcification.