Chronic pulmonary thromboembolic disease can cause severe pulmonary hypertension, which was called chronic thromboembolic pulmonary hypertension (CTEPH).Pulmonary hypertension is a progressive pulmonary vessel disease characterized by a sustained increase in pulmonary vascular pressure and remodeling.Overgrowth of pulmonary artery smooth muscle cells (PASMC) is a major cause for pulmonary vascular remodeling.Increased cytosolic Ca2+ concentration ([Ca2+]cyt) is involved in stimulating PASMC proliferation.The current study was designed to detect whether the PASMCs proliferation was enhanced from CTEPH patients, and if so, whether [Ca2+]cyt of PASMCs was also enhanced and to explore possible mechanisms.