For patients with pulmonary arterial hypertension (PAH) two first line therapies - iloprost inhalation (Ventavis) and bosentan (Tracleer) -- are available in Germany. A third substance, sildenafil, is already approved in the US and will be approved for this indication in the European Union soon. Patients with PAH can be stabilized or improved with a specific mono-therapy for a limited period of time only. Therefore, the question arises when and how to initiate treatment escalation. The available data from controlled clinical trials are insufficient to give a definite answer to these questions. Moreover, it is still unclear which combination of the above mentioned substances may be superior in the treatment of PAH. On the other hand, combination therapy is already reality in clinical practice. Based on this background experts from specialized centers dealing with PAH discussed the scientific basis of the role of combination therapy in PAH patients during a workshop held on April 22/23. 2005 in Wiesbaden. The goal of this workshop was to formulate a common position with regard to combination therapy of PAH on the basis of the available scientific data and clinical experience.