EEG with co-registered electrocardiography was recorded during at least two interictal epileptiform EEG discharges in each of 11 patients who later suffered from sudden unexpected death in epilepsy (SUDEP), and from another 11 age and sex matched patients, also with uncontrolled tonic-clonic seizures, drawn from the same centre who were still alive at the time of investigation (non-SUDEPs). A corrected QT interval for rate (QTc) was obtained and a mean value calculated for the period immediately prior to discharge, during discharge and immediately post discharge. Mean QTc was also obtained interictally without discharge. There was a significant (P = 0.01) increase in the mean QTc during discharge compared to that measured interictally without discharge for the whole population of SUDEPs and non-SUDEPs, and this was maintained for the SUDEPs alone (P = 0.02) but did not hold for the non-SUDEP group alone. Although reaching statistical significance, increases in mean QTc in SUDEP patients only exceeded currently accepted upper limits in one case, and then only marginally. The clinical significance of these findings merits further investigation.