Good-quality sleep is an important and frequently overlooked component of general health, but it is particularly essential to patients with epilepsy. Their sleep can be affected by seizures, concurrent sleep disorders and seizure treatment. Worsening sleep can result not only in poor daytime functioning but also potentially in worsening epilepsy. The effects of antiepileptic drugs (AEDs) on sleep are of particular concern. Some agents have detrimental effects on sleep, particularly benzodiazepines and barbiturates but also phenytoin and, possibly, carbamazepine. Others, especially gabapentin, seem to actually improve sleep quality. Much research in this area is confounded by the effects of seizures and concurrent conditions on sleep, making it difficult to isolate the direct effects of AEDs on sleep. But because AEDs have independent effects on sleep quality, the choice of an appropriate agent not only determines whether seizures are completely controlled but also whether the patient performs optimally on a daily basis.