Background: Data on the efficacy and safety of balloon pulmonary angioplasty (BPA) in Taiwanese patients with chronic thromboembolic pulmonary hypertension (CTEPH) are lacking. In this study, we evaluated the effects of BPA on clinical parameters including hemodynamics, echocardiography and functional status in patients with inoperable CTEPH in Taiwan. Methods: We retrospectively collected the clinical data of inoperable CTEPH patients who underwent ≥3 BPA sessions. Pulmonary hemodynamic parameters of right heart catheterization, echocardiography, 6-min walk distance and World Health Organization (WHO) functional class were collected and analyzed before and after BPA treatment. Results: A total of 59 BPA sessions were performed in 13 inoperable CTEPH patients. No periprocedural deaths or major complications requiring tracheal intubation with mechanical ventilation occurred. WHO functional class significantly improved in all 13 patients (P