In 47 patients with chronic obstructive pulmonary disease and 19 patients with idiopathic pulmonary fibrosis pulmonary haemodynamics were studied. Pulmonary arterial pressure was compared with non-invasive lung function tests, ecg and the chest X-ray. Correlations between pulmonary arterial pressure and some of those parameters were found. Investigations were repeated after 3 or 5 years depending on severity of pulmonary hypertension initially found. The progression of pulmonary hypertension was found. It was accompanied by intensification of non-invasive indices of pulmonary hypertension. More than half of patients with initially severe pulmonary hypertension (> or = 30 mmg Hg) did not survive 3 years.