The occurrence of high-risk cardiac arrhythmias during electrographic seizures has been proposed as a possible cause for sudden unexpected death in patients with epilepsy. Several anecdotal case reports have documented various cardiac irregularities during seizures. We reviewed simultaneous 24-hour electroencephalographic - electrocardiographic studies obtained by ambulatory cassette electroencephalography in 45 patients who experienced 106 electrographic seizures. An increase in heart rate was seen in 96% of seizures, while in four seizures, the rate was unchanged. Heart rate increase measured from 1 minute preictally to intraictal peak ranged from 0% to 160% (mean, 60%). The onset of tachycardia was usually within several seconds (before or after) of the seizure onset, and often persisted for several minutes after termination of the discharge. No difference was found in patients with lateralized vs generalized seizures. Neither ventricular ectopia, conduction defects, or bradycardia were observed during the ictal episodes. We conclude that ictal tachycardia is the rule during electrographic seizures, and that high-risk cardiac arrhythmias are uncommon.