Motivated in part by the significant toll of this disease, a conference on the Scientific Basis of Respiratory Therapy, co-sponsored by the American Thoracic Society and the Division of Lung Diseases, examined the current status of the use of oxygen therapy in chronic lung disease. The proceedings of the conference, published in the American Review of Respiratory Disease (Vol. 110, No. 6, December 1974), included a recommendation for clinical studies that would provide a critical assessment of the role of nocturnal oxygen therapy in the treatment of patients with chronic obstructive pulmonary disease. Low-flow oxygen, administered continuously, was known to benefit some patients with chronic hypoxic lung disease. However, low-flow oxygen administration for long periods of time is cumbersome, confining, and expensive. If nocturnal oxygen administration could be unequivocally demonstrated to be efficacious, then the advantages of convenience and cost would have a favorable impact on treatment of patients, and a rationale could be developed for testing this therapy in a larger group of patients.