At six centers, 203 patients with stabilized hypoxemic chronic obstructive pulmonary disease were evaluated hemodynamically during a continuous or 12-hour oxygen therapy program. Neither oxygen therapy program resulted in correction or near-correction of the baseline hemodynamic abnormalities. The continuous oxygen therapy group did show improvement in pulmonary vascular resistance, pulmonary arterial pressure, and stroke volume index. The improvement in pulmonary vascular resistance was associated with improved cardiac function, as evidenced by an increase in baseline and exercise stroke volume index. The nocturnal oxygen therapy group showed stable hemodynamic variables. For both groups, changes in mean pulmonary artery pressure during the first 6 months were associated with subsequent survival after adjustment for association with the baseline mean pulmonary artery pressure. Continuous oxygen therapy can improve the hemodynamic abnormalities of patients with hypoxic chronic obstructive pulmonary disease. The hemodynamic response to this treatment is predictive of survival.