Objective. To study the pathomorphosis of idiopathic generalized epilepsies (IGE) in a large population of adult patients with long-term follow-up. Material and methods. The study involved 1480 patients with epilepsy, including 281 patients with IGE. Results. In 26 patients with childhood absence epilepsy (CAE), age-related changes in disease course have been particularly pronounced. None of the patients had frequent typical absences («pyknolepsy») at the time of the survey. Sixteen of 26 patients had predominantly rare generalized tonic-clonic seizures in combination with occasional absences or myoclonic jerks, while in 2 patients there was the transition from the DAE to juvenile myoclonic epilepsy (JME). The EEG recorded in the «adult» age showed the level of epileptiform activity in only 12 patients out of 26 (in 2 patients only during nighttime video-EEG-monitoring). EEG changes resembled a «juvenile» form of epilepsy. At the time of completion of the study, 13 patients were free of seizures and only 5 of 26 patients with DAE did not require treatment with antiepileptic drugs. In patients with Jeavons (n=14) and Tassinari (n=1) syndromes, the disease did not change over time. Conclusion. The pathomorphosis of IGE with childhood onset depends on the certain epileptic syndrome.