All patients who present with severe headaches merit careful medical and neurologic evaluation, and many require neuroimaging studies or lumbar puncture. To avoid missing the occasional seriously ill patient among the large number of patients with relatively benign headaches, physicians must maintain a high index of suspicion and a familiarity with the differential diagnosis. Patients with severe acute headaches must be evaluated for subarachnoid hemorrhage and bacterial meningitis. Temporal arteritis must be excluded in all older patients with recurrent headaches of recent onset. Trigeminal neuralgia and cluster headache usually do not signify serious underlying disease, but the severity of the pain mandates rapid diagnosis and institution of therapy. Migraines are extremely common and often mislabeled as tension or sinus headaches. All primary care physicians should be able to recognize the many faces of migraine and be familiar with symptomatic and prophylactic therapy. Difficult cases should be referred to a neurologist for ongoing care.