Little is known about the cognitive effects of chronic epilepsy in older adults. To better characterize cognitive impairment in seniors with epilepsy, we compared cognitive performance of 26 seniors with epilepsy with that of 26 well-matched patients with mild cognitive impairment (MCI) and 26 well-matched healthy older adults. Participants completed neuropsychological testing with the Dementia Rating Scale (DRS), Logical Memory, and CFL Word Fluency. There were no significant demographic group differences, although seniors with epilepsy had higher self-reported depression. Seniors with epilepsy performed below controls on virtually all neuropsychological tests, and performed below patients with MCI on DRS Total score, Initiation/Perseveration, and CFL Fluency. Seniors with epilepsy on antiepileptic drug (AED) polytherapy had the most severe cognitive deficits, whereas seniors with epilepsy on AED monotherapy were comparable to cholinesterase inhibitor-naïve patients with MCI. This study emphasizes the clinical importance of cognitive impairment in seniors with epilepsy and highlights the need for future studies addressing causes and treatment of cognitive impairment. © 2005 Elsevier Inc. All rights reserved.