A healthy brain requires balancing of waking and sleeping states. The normal changes in waking and sleeping states result in neurophysiological conditions that either increase or decrease the tendency of seizures and interictal discharges to occur. This article reviews the manifold and complex relationships between sleep and epilepsy and discusses treatment of the sleep-related epilepsies. Several forms of epilepsy predominantly or exclusively manifest during sleep and seizures tend to arise especially from light NREM sleep. Diagnostic interictal epileptiform discharges on the electroencephalogram are also most likely to be activated during deep NREM sleep stage N3. Epileptiform discharges and antiepileptic medications may in turn detrimentally impact sleep. Co-morbid sleep disorders also have the potential to worsen seizure control. Sleep has an important key association with sudden unexpected death in epilepsy (SUDEP). Further research is necessary to understand the complex relationships between sleep and epileptic disorders and their treatments.