We have studied the fibrillary inclusions (including filamentous inclusions) in the nerves of dog stomach. Fibrillar inclusions, which consist of the sheaves of parallel osmiophilic fibrils (about 90 Å in width) and which are completely devoid of distinctive interconnections between the filaments, were found only in the preterminals of the vagus and not in the nerve cells of the stomach, after electric stimulation. Of 15 stomachs in which the vagus was electrically stimulated, only one stomach contained this type of inclusions. From these results, the origin of such fibrillary inclusions was not clear. Other types of fibrillar inclusions were found in the nucleus of the nerve cells : there were nuclear bodies and rod-shaped inclusions. The former was the fibrillogranular bodies, onion-like whorl bodies and “Marinesco bodies”, and the latter seemed to be a variant of the former and a paracrystalline inclusion. They were frequently observed in control stomachs and after electric stimulation of the vagus and sometimes after vagotomy.In the perikaryon, both string-like inclusions and paracrystlline inclusions were found : the former was found in only one of 65 stomachs, whereas the latter was frequently found after longer electric stimulation but rarely found after vagotomy. The results suggest that neurofibrillary changes are probably one of the early degenerative changes in the myenteric plexus of the stomach. The nuclear bodies may be related to the neuronal activity, whereas paracrystalline inclusions are probably one of the early degenerative changes in the myenteric plexus of the stomach.