Juvenile myoclonic epilepsy (JME) is a widely recognized presumed genetic, electroclinical idiopathic generalized epilepsy syndrome. The prevalence of JME in large cohorts has been estimated to be 5% to 10% of all epilepsies and around 18% of idiopathic generalized epilepsies but may be lower in some settings. There is a marked female predominance. However, some of the basic epidemiology of JME is not well known, possibly because the syndrome is not sharply defined. A questionnaire study about the diagnostic criteria for JME suggests that diagnosis of JME can be made with the history of myoclonus plus a single generalized tonic-clonic seizure plus generalized fast spike-waves or polyspike-waves on the EEG. However, until these diagnostic criteria are fully accepted, the detailed epidemiology of JME will remain imprecise.