A case of spontaneous intracranial artery dissection (IAD) of the anterior circulation is reported. A 32-year-old man developed left hemiparesis with headache. Angiographies (AGs) showed progressive occlusion of the distal end of the right internal carotid artery. He underwent a superficial temporal artery-middle cerebral artery anastomosis 20 days after his initial symptoms. He improved gradually after operation. The prognosis and treatment of IAD are discussed. The authors conclude that cases with IADs of the anterior circulation should be followed up by cerebral AG or magnetic resonance angiography and that early bypass surgery should be considered to prevent massive cerebral infarction in some cases.