In order to study how deafferentation or deefferentation of the tongue affects chewing, this experiment was carried out. Male Wistar rats weighing 400∿600 g were used. The connector pedestal was fixed by dental cement on the center of the cranial bone under anesthesia. Monopolar EMG electorodes were sewed on the left and right masseter muscle and the wires coated with Teflon from the EMG electrodes were led to the connector pedestal under the skin. The connector pedestal and the input box of amplifier were connected with the fine spiral cords. One week after setting the connector pedestal, EMG activities of both masseter muscles during feeding were recorded and displayed by the oscilloscope and recorder, and integrated by minipolygraph, and these EMG records were used as control. Rats could move freely in the cage during recording EMG. After a week from recording control EMG, bilateral lingual nerves (LN), unilateral hypoglossal nerve (UHN), bilateral medial branches (MB) and bilateral lateral branches (LB) of hypoglossal nerves were severed under anesthesia. EMG activities of both masseter muscles in feeding were recorded once a week from 3 days after severance of the nerves or nerve branches of the tongue and these records were compared with control EMG. The main findings were summarized as follows. 1. When LN, UHN and LB were severed, feeding behavior and food intake in most rats did not change. But, all rats with severed MB could not take the pellets just after severance of one. 2. After severance of LN, duration of discharge during chewing was slightly prolonged. Amplitude, EMG activities, cycle, and interval of the both masseter muscles during chewing however did not change. 3. After severance of UHN, amplitude and EMG activities on severed side were reduced obviously, and duration of discharge on the intact side was shortened. Others however did not change. 4. After severance of MB, cycle and interval were disturbed and amplitude, EMG activities, and duration were reduced, but these changes were recovered with lapse of time. After severance of LB, EMG activities were slightly reduced. Others however did not change.