Increased intracranial pressure developed in a mentally and physically normal patient following ingestion of 30 glasses of water as a voluntary preparation for ultrasonic gynecological examination. Hyponatremia resulted and induced brain edema which provoked increased intracranial pressure. Hyponatremia was treated by intravenous infusion of hypertonic NaCl and mannitol solutions. Corticosteroids were added and continued for a week. The patient totally recovered 4 days after admission.