Primary pulmonary hypertension (PPH) is a fatal cardiovascular disease characterized by increased pulmonary vascular resistance and progressive right heart failure. It is associated with a very high morbidity and mortality rate. The therapeutic effects of current pharmacological management of PPH are limited. Recent studies have demonstrated that endothelial dysfunction and cell loss play a critical role in the pathogenesis of PPH. Emerging evidence also shows that circulating endothelial progenitor cells instigate new vessel formation via vasculogenesis and revascularization, and provide ongoing endothelial repair by homing to site of endothelial damage. We hypothesized that autologous endothelial progenitor cells transplantation may be a feasible adjunctive therapeutic option for PPH.