Fibromuscular dysplasia (FMD) is a noninflammatory, nonatherosclerotic arterial disease that can affect any artery but most commonly affects the renal, carotid, and vertebral arteries, predisposing to stenosis, aneurysm, dissection, and/or tortuosity. 1-3 While headache is a common symptom reported by patients with FMD, little is known about this relationship. 4,5 The etiology of FMD is not known, nor is it understood why such a high percentage of patients with FMD experience headaches. 6 In addition to FMD, patients with associated vascular abnormalities, such as intracranial aneurysm and cervical carotid and vertebral artery dissection, also commonly experience headache. 5,7,8 The aim of this study was to report the frequency and characteristics of headache in a cohort of patients enrolled in the United States Registry for FMD and to identify clinical factors associated with the presence of this symptom. From 2009 through 2016, 1433 adult patients 18 years of age and older were enrolled in the Registry. Eligibility for enrollment was determined by site investigators based on identifying the characteristic appearance of multifocal or focal FMD from vascular imaging in at least one vascular bed. 2,5 Eligible subjects provided written informed consent. Demographic and clinical data, family history, headache-related variables, presenting signs and symptoms at the time of FMD diagnosis, and medications taken at the time of enrollment were recorded. An assessment of headache at initial Registry enrollment included query for presence of headache, type of headache (migraine or other), frequency of headache, whether headache was associated with menses, and whether headache(s) required suppressive medication. The Institutional Review Board (IRB) at the University of Michigan, the Data Coordinating Center for the US Registry of FMD, approved this study (HUM00022250). In addition, all participating sites in the Registry obtained individual institutional IRB approval. Patients were categorized into two groups: those with and those without reported headaches at the time of Registry enrollment. Univariate analysis was conducted by comparing demographics, past medical history, symptoms and signs at time of FMD diagnosis, arterial bed involvement, and family history between the two groups using Student's