A 48-year-old woman exhibited hyperperfusion soon after undergoing a successful clip operation involving multiple clip placement for a giant internal carotid artery (ICA) aneurysm. Intraarterial digital subtraction angiography demonstrated a left paraclinoid giant aneurysm. Multiple clips were placed to obliterate the aneurysm during a 7-minute temporary ICA occlusion. Intraoperative Doppler ultrasound flowmetry showed that the blood flow through the ICA distal to the aneurysm increased from 71.6 ml/minute before clipping to 123.3 ml/minute after. The patient exhibited right hemiparesis and motor aphasia after the operation. Postoperative imaging studies revealed an increase in perfusion and diffuse edema in the left cerebral cortex. The symptoms and diffuse brain edema gradually resolved. In this case, increase in blood flow through the ICA distal to the aneurysm may have played an important role in the circulatory disturbance.