We aimed to review recent prospective and cross-sectional studies regarding the gradual and chronic effects of (cumulative) seizures on cognition. In contrast with the increasing evidence of structural changes in the brain associated with repeated seizures, its functional repercussions remain unclear. Methodological difficulties of cross-sectional and prospective studies are addressed. It appears that all but one of the prospective studies available on children are limited to measures of intelligence. Most studies revealed no significant adverse effects, although there appears to be a subgroup of about 10-25% of children that shows a clinically significant intellectual decline. Children with generalized symptomatic epilepsies, frequent seizures, high antiepileptic drug use, and early onset of epilepsy appear at risk, although psychosocial factors may also play an important role. Five of the six prospective studies on adults report evidence of a mild decline in cognition in patients with a (longstanding) history of pharmacoresistant epilepsy. The adverse effect on cognitive abilities, memory in particular, seems somewhat more robust than that on measures of intelligence. A significant association between cognitive decline and seizure related variables is rarely substantiated in prospective research and cross-sectional studies show contradicting results. Taken together, the data suggest a mild but measurable decline of intellectual performance in children and adults. Decline of specific cognitive abilities in children is impossible to evaluate given the very little data available. In adults, memory appears to be the most vulnerable cognitive function. Due to many confounding variables, the effect of seizures per se is difficult to estimate, but appears limited.