The state-of-the-art of oxygen delivery to the home has evolved remarkably in the past 25 years. Oxygen is established as not only safe but effective in selected patients with advanced COPD. Oxygen clearly has been shown to improve both the length and quality of life in many patients. Hospitalizations can be reduced by the use of home oxygen therapy. This appears to be most likely in ambulatory patients receiving long-term oxygen from portable liquid systems. It is likely that further advances will make home oxygen more suitable, acceptable, and perhaps less costly for a growing number of patients with progressive chronic respiratory diseases in whom significant hypoxemia and organ system damage are present.