Radiologists have become important members of a multidisciplinary team aimed at treating stroke. New studies such as the NINDS (National Institute of Neurological Disorders and Stroke) intravenous and PROACT II (prolyse in acute cerebral thromboembolism II) intra-arterial thrombolytic trials for acute stroke have focused attention on the need for rapid management. Radiologists play a key role in the diagnosis and selection of patients who may benefit from these therapies. We review current issues in the computed tomographic and magnetic resonance imaging diagnosis of acute stroke and the data supporting the various treatment options.