A value of pulmonary artery catheterization, exercise test and blood oxygenation at sleep was assessed. Such tests are considered as the additional possibility for classifying the patients with chronic obstructive disease, with moderate hypoxia, to the treatment with oxygen at home. Hemodynamic tests have shown pulmonary hypertension in 73% of patients. Clinical evaluation of the cor pulmonale seemed satisfactory. A decrease in arterial blood oxygenation during exercise below 88%, being a border value classifying to the treatment with oxygen at home, was found in 82% of patients. Marked decrease in blood oxygenation at sleep has been characteristic feature of all patients. Exercise test and oximetry at night may also valuable for classifying the patients to the treatment with oxygen under home conditions.