Unexpected sudden death is a common event in otherwise healthy epileptics, though its etiology has remained unclear. Many authors have suggested cardiac arrhythmias as the cause, and limited data in humans and animal studies have supported this. However, autopsy series in humans have shown pulmonary edema, a phenomenon not compatible with a sudden arrhythmic death, as a possible cause. We developed a model of status epilepticus in unanesthetized, chronically instrumented sheep in which sudden death and pulmonary edema occur. Catecholamine levels and seizure type and duration did not differ between animals dying suddenly and those surviving. Benign arrhythmias were generated in all animals; in no case did an arrhythmia account for the death of an animal. Striking hypoventilation was demonstrated in the sudden death group but not in the surviving animals. Differences in peak left atrial and pulmonary artery pressures, and in extravascular lung water were also demonstrated; pulmonary edema did not account for the demise of the sudden death animals. Thus, our model of epileptic sudden death supports a role of central hypoventilation in the etiology of sudden unexpected death and confirms the association with pulmonary edema. The importance of arrhythmia in its pathogenesis is not confirmed.