This article reviews the existing literature of the common anatomic and physiologic aspects of cluster headache and sleep-related breathing disorders to point out evidence suggesting potential therapies beneficial for both maladies. A search of PubMed, as well as relevant textbooks, was conducted using the terms cluster, headache, sleep, apnea, pain, and chronobiology to find any previously published work that may connect the two disorders. Relevant references in the literature were also investigated. As a group, cluster headache patients tend to have a higher incidence of sleep-related breathing disorders as compared to the noncluster headache population. While commonalities in anatomy and physiology exist, robust evidence linking the two disorders is currently lacking. Many people are unaware that they suffer with a sleep-related breathing disorder. The high incidence of these two disorders occurring together should prompt the clinician who treats cluster headache patients to be acutely aware that a yet undiagnosed sleep disorder may also be present. Keywords: cluster headache, hypercapnia, hypoxia, sleep apnea, sleep-related breathing disorders