Dizzy patients present a significant diagnostic challenge to the emergency clinician. The discrimination between peripheral and central causes is important and will inform subsequent diagnostic evaluation and treatment. Isolated vertigo can be the only initial symptom of a posterior circulation stroke. The sensation of imbalance especially raises this possibility. Research involving strokes of the posterior circulation has lagged behind that of the anterior cerebral circulation. Investigations of the last 20 years, using new technologies in brain imaging in combination with detailed clinical studies, have revolutionized our understanding of the clinical presentation, causes, treatments, and prognosis of posterior circulation ischemia.