This local, prospective, non-interventional, company sponsored, multi-center, single-cohort study includes patients treated with Ventavis for PAH. A total of 270 patients (valid for safety analysis) is planned to be enrolled in 5 years. Target population is patients with PAH diagnosis. This study is performed as an all-patient investigation, therefore all patients who receive Ventavis treatment for PAH need to be registered. The treatment should be performed based on the product label in Japan. The standard observation period will last for 12 months from starting Ventavis treatment. In addition, the extension observation will be carried out as long as Ventavis treatment continues or at most for more 4 years. The standard observation points are 3 month and