Hemodynamic values obtained during right heart catheterization in about 35 patients with chronic bronchitis were compared with the same variables 3.3 years later (range, 2 to 5 years). In the group of 13 patients with mean pulmonary arterial pressure less than 20 mm Hg at the first catheterization, the average value was 15.8 mm Hg at rest and 25.2 mm Hg during moderate exercise at the first investigation, and 16.9 and 26.3 mm Hg, respectively at the second catherization; the changes were not significant. In the group of pulmonary hypertensive patients, the mean pulmonary arterial pressure was 27.0 mm Hg at rest and 44.1 mm Hg during moderate exercise at the first catheterization, and 26.8 and 38.9 mm Hg, respectively, at the second catheterization. Thus, even in this group, there was no deterioration in pulmonary hemodynamics, because there was no significant change in right or left filling pressure, or in cardiac output. There was, however, a marked decrease in systemic arterial pressure, which was significant in the group with pulmonary hypertension. This decrease in left ventricular afterload could be partly responsible for the stabilization of pulmonary hemodynamics, and it could be due to the peripheral vasodilating effect of hypoxia and hypercapnia.