Sleep and epilepsy have bidirectional relationships, and various endocrine interactions. Besides the commonly observed increase in seizure frequency in association with sleep loss or with sleep disorders, such as sleep apnea, seizures themselves may lead to sleep fragmentation. Furthermore, nocturnal seizures may be associated with more severe and longer lasting respiratory consequences, as well as higher risk of sudden death. It is common for sleep to change during pregnancy in relation to endocrine changes and these changes may in turn affect seizure frequency. Overall, estrogens may have excitatory effects and may increase the consolidation of wakefulness and decrease REM sleep duration. Progesterone tends to have a sedative effect and the decrease in level may lead to more complaints of insomnia pre-menstrual and after menopause. Common sleep disorders are discussed. Obstructive sleep apnea becomes much more common after menopause, and sometimes may be seen in the third trimester of pregnancy as a result of weight gain. Restless legs syndrome is more common in pregnancy. Overall, insomnia is more common in women. Consideration should be given to comorbid primary sleep disorders whenever symptoms of insomnia or hypersomnolence are reported by patients with epilepsy.