All of the established antiepileptic drugs (AEDs) can produce cognitive side effects, which are increased with polypharmacy and with increasing dosage and anticonvulsant blood levels. However, cognitive side effects are usually modest for AED monotherapy with anticonvulsant blood levels within the standard therapeutic ranges. Further, these effects are offset in part by reduced seizure activity. Controversy exists regarding possible differential cognitive effects of AEDs. A large portion of the literature examining the comparative cognitive effects of AEDs is limited by inadequate study designs. When these design flaws are considered, there is no convincing evidence of clinically significant differences in cognitive side effects of AEDs except possibly for bromide, phenobarbital and benzodiazepines. The role of cognitive side effects should be kept in proper perspective when choosing AED therapy. The cognitive side effects of anticonvulsant drugs may be overt but many times are rather subtle. It is important though to be able to recognize these effects and to put them into perspective as to how they affect our patients.