A Long-term Extension Study of Riociguat in Patients With Symptomatic Pulmonary Arterial Hypertension.

Inclusion Criteria: * Patients diagnosed with Pulmonary Arterial Hypertension (PAH) participating or having participated in the Bayer-sponsored studies 12935, 16719 or 18588, who have completed the main study phase and are still being treated with riociguat (either while still being on treatment with the respective study drug or by commercial means with Adempas) and who, in the opinion of the investigator, are expected to continue to have an overall positive benefit/risk from continuing treatment. * Women and men of reproductive potential must agree to use adequate contraception when sexually active. This applies for the time period between signing of the informed consent form and 30 days after the last administration of study drug. Exclusion Criteria: * Ongoing serious adverse event (SAE) from originating study that is assessed as related to riociguat * Pregnant women or breast-feeding women * Any contra-indication to Adempas treatment listed in the BAY63-2521 / Riociguat Investigators's Brochure * Concomitant participation in another clinical study with the study drug * Patients with pulmonary hypertension associated with idiopathic interstitial pneumonia (PH-IIP)