Effect of 12 month steroid therapy on pulmonary circulation at rest and during exercise was assessed in 24 patients with histologically confirmed stage II and III pulmonary sarcoidosis. Pulmonary hypertension was found in 3 patients before starting therapy. In the remaining 21 pulmonary artery pressure was within normal limits. In 18 of these an abnormal increase of pulmonary arterial pressure during exercise was found. After 12 months of steroid therapy in all except 2 patients radiological regression was observed. In most patients pulmonary function improved. Normal pulmonary arterial pressure was found in 22 patients. An abnormal increase of pulmonary arterial pressure during exercise was seen in 12 patients. No correlation could be demonstrated between radiological evaluation, respiratory function and effect of steroids on pulmonary circulation.