Background: Secondary cluster headache following carotid endarterectomy (CEA) is a rare condition and may help us understand the pathophysiology of primary cluster headache. Summary: We describe 2 patients diagnosed with cluster headache, fulfilling the ICHD-IIIB criteria, following CEA. Neither of the patients had headache prior to surgery. They both responded to treatment with oxygen and verapamil. Recent medical literature does not describe any definite cases of cluster headache following CEA. Cluster-like headache has been reported in several studies in the 1990s. Recent studies in primary cluster headache patients show evidence for a central origin of cluster headache in which no peripheral drive seems necessary. Key Messages: Our findings may provide more insight into the pathophysiology and show how a peripheral cause may lead to cluster headache. We hypothesize a role of the trigemino-autonomic reflex. Damage to the carotid artery may activate this reflex and trigger cluster headache. Injury to the internal carotid artery may unleash attacks in patients who are predisposed to develop cluster headache. Further study on the subject is needed to resolve this issue.