The minute volume of ventilation was determined in 35 patients with pulmonary emphysema, as they inhaled air or 40% oxygen during and after exercise. The average minute volume increased 38% following exercise with oxygen, as compared to 60% with air over the resting control. Exercise with oxygen induced less dyspnea than with air. At rest, the minute volume while breathing 100% oxygen was 16% lower than while breathing air. A program of graded walking exercises while inhaling 40% oxygen resulted in an increase in exercise tolerance of patients with pulmonary emphysema. Signs of uncompensated respiratory acidosis were avoided in most instances, while hypoxia and cardiac decompensation complicating this disease were improved by supervised oxygen inhalations using flows of 1 liter per minute, followed by daily increments of 1 liter per minute up to 5 liters per minute, by nasal cannula.