Summary:: The relationship of a number of epilepsy variables to cognitive decline is reviewed. Underlying brain damage, seizure age of onset, type and frequency, and anticonvulsant drugs are all considered. Two investigations in which subgroups of patients with intellectual deterioration have been compared to those without such deterioration are presented, and certain conclusions are reached with respect to the most important factors that relate to decline. Recurrent tonicclonic seizures, head injury, the prescription of phenytoin, and low folic acid levels were all related to cognitive decline in one or both of the studies, and the implications of this for the management of epilepsy are noted.