Transient abnormalities of autonomic nervous system function are observed during almost every generalized tonic-clonic seizure and include disruptions in blood pressure, cardiac arrhythmias and apnea. An increasing body of literature indicates that epileptogenic discharges, even without accompanying clinical seizure activity, can produce a spectrum of autonomic abnormalities. Marked changes in blood pressure and cardiac rhythm occur in patients paralyzed with neuromuscular blocking agents and subjected to electrical shock or intravenous pentylenetetrazol. Similar changes are observed in patients with focal temporal lobe discharges. There is also experimental evidence suggesting that in addition to the well known effects of generalized seizure discharges, interictal discharges can produce effects upon the cardiovascular system. Neurogenic pulmonary edema may be another autonomic dysfunction associated with seizures. The phenomenon of unexplained sudden death in persons with epilepsy, which accounts for up to 15% of mortality in this group, may be a result of some unexplained irreversible disruption of autonomic homeostasis in the face of all these forces of electrical disorganization. Paradoxically, some persons manifest cardiovascular autonomic dysfunction with consequent seizures which are phenomenologically very similar to those of cerebral origin. It is important to consider performing Holter monitoring in patients with epilepsy of unknown cause and 24 h ambulatory electroencephalograms in patients with unexplained cardiac arrhythmias.