Sudden unexplained death in epilepsy have been reported in epilepsy patients. A causal relationship with the administration of antiepileptic drugs has not been established. The most important known risk factor for sudden unexplained death in epilepsy (SUDEP) is the occurrence and frequency of generalized tonic-clonic seizures (GTCS). Twenty-seven patients with only GTCS were enrolled in the conversion to monotherapy study. In this study, two patients with only GTCS had SUDEP. Due to the potential increased risk of SUDEP in patients with only GTCS in a trial setting, the 1 remaining patient with only GTCS was withdrawn from this study.