Aphasia is an acquired disorder of language resulting from focal or diffuse injury to the dominant cerebral hemisphere. Investigation of aphasia provides insight into the complex organization of higher cerebral function. Major motor aphasia is characterized by effortful, dysfluent speech with relatively spared comprehension and is localizable primarily to anterior cortical structures. By contrast, aphasia that produces predominantly sensory features is manifested by fluent, often nonsensical speech littered with paraphasic errors and is characterized by poor comprehension. Major sensory aphasias are localized primarily to posterior parietal and temporal regions of the brain. The minor aphasic syndromes such as conduction aphasia and the transcortical aphasias are produced by anatomically mare variable lesions and often appear in the setting of recovery of the major aphasias. In this article, the salient features of all the aphasic syndromes are described in anatomical and clinical detail with reference to groundwork historical observations as well as the modern imaging techniques that have futher advanced our understanding of acquired language dysfunction.