Inhaled normobaric oxygen is an essential abortive treatment of cluster headache. Recognition of its efficacy for cluster headache goes back a half a century, but very little has actually been written on the use of inhaled oxygen for cluster headache. This article examines various issues regarding inhaled oxygen and cluster headache, including efficacy, proposed mechanism of action, utilization, and the economics of oxygen usage for cluster headache patients. Much of the data analyzed comes from the recently published United States Cluster Headache Survey. This is the largest study of cluster headache patients ever published and is the first study to focus on inhaled oxygen and cluster headache in a large, non-clinic-based population.