Background & Objectives – Angiotensin is as an important hormone involved in several vascular pathologies. However, the molecular mechanism of angiotensin in vascular calcification is not established yet. Cystein-rich angiogenic protein 61 (CYR61, CCN1), an angiogenic immediate early gene, which is associated with vascular restenosis, angiogenesis, and tumor growth, is reported to be regulated by angiotensin II (Ang II) in vascular smooth muscle cells (VSMCs). And CYR61 expression has been suggested to play an important role in Wnt3A-induced osteoblast differentiation of mesenchymal stem cells. Therefore, we hypothesized that the CYR61 may play a role in VSMCs calcification by Ang II. Methods and Results – Primary cultures of VSMCs were prepared from thoracic aortas of 20 weeks aged male C57BL6 mouse. Six to seven passages of VSMCs were incubated at 37��� in DMEM containing 10% FBS with 1% antibiotics/antimycotics solution. To evaluate the effect of CYR61 on calcification, VSMCs were transfected with adenoviral vectors expressing CYR61 (Ad-CYR61) at 100 multiplicities of infection (mois). As a control, an adenoviral vector expressing only green fluorescent protein (Ad-GFP) was used. We evaluated the calcification of VSMCs by von Kossa staining for calcium mineral and RT-PCR for bone morphogenetic protein2 (BMP2) expression. CYR61 gene transduction activates expression of BMP2, mediator of vascular calcification, and promotes mineralization of VSMCs. When VSMCs were treated with Ang II (10-7M), BMP2 expression from VSMCs increased significantly compared to the control, followed by accelerated mineralization. This Ang II-induced osteogenic differentiation was significantly reduced by co-transfection of antisense-CYR61 adenovirus (Ad-As-CYR61), suggesting these effects of Ang II was mediated by CYR61. Conclusions – Ang II was found to stimulate osteogenic differentiation and mineralization of VSMCs via CYR61 activation.