Background: Juvenile myoclonic epilepsy (JME) is classified as primarily generalized epilepsy and as such is assumed to lack an anatomic substrate. Although neurochemical abnormalities are probable, few studies have investigated whether they exist in JME. Animal data and the high incidence of myoclonic seizures in serotoninintoxicated patients suggest that the serotonin system may be disturbed in JME.Objective: To test the hypothesis that JME is associated with a disturbed serotonin system and that this disturbance could be reflected in altered serotonin 1A receptor binding. Design:The serotonin 1A receptor binding potential (BP) was measured with positron emission tomography and serotonin 1A receptor antagonist carbonyl-carbon 11-WAY-100635. The BP was calculated using a reference tissue model in several limbic and neocortical regions and the raphe nuclei.