We studied clinical-electroencephalographic features in different forms of idiopathic generalized epilepsies (IGE) with variable phenotype in adulthood respective from type of course of the disease.The study included 44 patients with juvenile absence epilepsy (JAE), 97 patients with juvenile myoclonic epilepsy (JME) and 102 patients with IGE with isolated generalized tonic-clonic seizures (GTCS).Presence of absences and myoclonias, GTCS at awakening, interictal epileptiform activity (IEA) under photostimulation and in the period of slow sleep were shown as predictors of GTCS relapse in adults.Detection of clinicalelectroencephalographic markers of poor prognosis of IGE in adulthood was a factor excluding achieving the non-medication remission and withdrawal of antiepileptic drugs (AED) could heighten risk for GTCS relapse.