A variety of aphasic patients were studied to determine the relationship betweeen lesion size, as demonstrated by cranial computed tomography (CCT), and the type of aphasia, as classified by the Boston Diagnostic Aphasia Examination (BDAE). CCT demonstrated a variety of lesions. Those in nonfluent Broca's aphasics and fluent Wernicke's aphasics were separable into pre-Rolandic and post-Rolandic areas, respectively. Conduction, global, and anomic aphasics had different lesion sites. Correlation of lesion location by CCT with aphasia type supports Geschwind's concepts of aphasia.