Two right-handed patients with clinical evidence of major infarction in the territory of the left anterior cerebral artery developed a profound but transient aphasia characterized by (1) a striking dissociation between intact repetition and grossly disturbed spontaneous conversational speech, (2) an absence of phonemic paraphasia, (3) a lack of speech inhibition and (4) relative preservation of conformation naming and comprehension. Despite the initially profound motor aphasia, servicable spontaneous conversational speech returned in two to three months. However, more subtle changes in the form of lack of speech initiative and difficulties in narrating stories and describing complex pictures, remained many months after the onset. In these patients the major features of the disturbance could not be explained only on the basis of an interruption of the downgoing pathway from the dominant motor speech area, and in fact, may have been due to damage to the superior and mesial pre-motor area (particularly the supplementary motor region), an area that has been shown to play a role in processes which govern the initiation, continuation and inhibition of speech.