Follow-up data for 81 consecutive patients with primary pulmonary hypertension (PPH) and pulmonary hypertension related to connective tissue diseases or liver cirrhosis, entered into a multicenter registry in Berlin between 1/96 and 11/99, are described. At entry into the registry the diagnosis of PPH was known for 22 +/- 32 months. Hemodynamically, these patients were characterized by a right atrial pressure of 8.6 +/- 5 mmHg, a mean pulmonary arterial pressure of 58.9 +/- 17 mmHg, a cardiac index of 1.8 +/- 0.6 l/min/m2 and a pulmonary vascular resistance of 1574 +/- 787 dyn x s x cm-5. In about one third of the patients, a restrictive and/or obstructive pulmonary physiology was found while the majority showed signs compatible with small airway disease. Furthermore, diffusion abnormalities were found in about 65% of the patients. When added to conventional medical therapy the treatment with inhaled or continuously infused prostanoids represents a major improvement in the treatment of patients with PPH. Aerosolized iloprost therapy was started in 51 patients and was continued for 12 and 24 months in 20 and 6 patients, respectively. This therapy was well tolerated without any significant changes in pulmonary function or signs of toxicity. About 25% of these patients had to be switched to continuous intravenous therapy due to progressive clinical and hemodynamic deterioration. About two thirds of these "rescue patients" could be stabilized on intravenous therapy and discharged from the hospital. Based on the currently available evidence, the continuous infusion of prostanoids represents an important part of the standard therapy in the treatment of patients with PPH. These first long-term data on inhaled iloprost therapy in this patient group illustrate the potential value of this well-tolerated and effective treatment within the concept of a differentiated treatment plan for patients with PPH. However, the true importance of prostanoid inhalation in comparison to continuous intravenous therapy in PPH remains to be determined in randomized controlled trials.