The authors investigated 8 cases of infarction in the territory of the anterior cerebral artery (5 cases in the left hemisphere, 2 in the right and 1 bilateral) as to their language functions. Serial examinations on the language function were performed clinically and by using SLTA and Syntax Test of Aphasia from the acute stage. The lesions were confirmed by CT scan and cerebral angiography.     The characteristics of the symptoms were :     1) a striking suppression of spontaneous speech (mutism) in the acute stage,     2) intact or minimal impairment of verbal and literal comprehension and repetition,     3) good recovery of language function,     4) persistance of some difficulty in speech initiation and in syntactic ability,     5) association with a generalized decrease in voluntary movements (akinesia),     6) these dysfunctions were equally demonstrated in each hemisphere lesion,     7) when the lesion in the left hemisphere extended beyond the medial frontal region (two cases), it showed persistent classical transcortical motor aphasia.     We concluded that the language disorders due to the lesion limited to the medial frontal region might be different from the classical transcortical motor aphasia because of their occurrence also in the non-dominant hemisphere lesion and good recovery.     It is suggested that these disorders are a part of generalized akinesia caused by dysfunction of each medial frontal cortex especially that associated with the supplementary motor area.