Reversible cerebral vasoconstriction syndrome is a common, increasingly recognized cause of thunderclap headache. Most patients have some type of trigger that precedes the onset (e.g., orgasm, physical exertion, Valsalva maneuvers, exposure to vasoconstrictive medications) followed by multiple short-duration thunderclap headaches that occur over days to weeks. Physical examination is often without focal neurological deficits. Brain computed tomography may be normal, or show a convexal subarachnoid hemorrhage. Angiography shows multifocal areas of cerebral arterial vasoconstriction, although can be normal early in the course. The vasoconstriction is reversible and repeat angiography in three months will show normalization. The clinical outcomes are usually good despite some patients having hemorrhagic or ischemic strokes. Treatment is primarily analgesics and avoidance of triggers. Triptans, steroids and immunosuppressive agents, which are sometimes used if migraine or central nervous system angiitis is suspected, should be avoided. Improved recognition of RCVS will likely lead to earlier diagnosis and minimize potentially harmful empiric treatment strategies.