Clinical course and results of therapy were analysed in the group of 92 children, aged between 3 and 9 years, with diagnosed Lennox-Gastaut syndrome. The obtained results of an analysis have shown that Lennox-Gastaut syndrome origin is not clear--causative factor can not be established in 1/3 of patients whereas in 1/2 of them abnormal course of pregnancy and perinatal period is noted. Together with seizures of various origin, other focal neurological symptoms, mental retardation and abnormalities in CT scans of the brain are frequently seen in patients with Lennox-Gastaut syndrome. Clinical course, prognosis and results of therapy are largely dependent on the degree of mental development before the onset of epileptic seizures, course of pregnancy and perinatal period, and the time of therapy. Children with Lennox-Gastaut syndrome require relative polytherapy in which valproic acid derivatives are predominating together with benzodiazepines, and temporary corticosteroids. An improvement was achieved in about 30% of the treated children. Prognosis in the remaining 70% of children is rather poor. Irregular administration of drugs, frequent changes of anti-epileptic agents, too low doses and abnormal environmental effects (abnormal parental attitudes) affect the results of therapy. An emphasis is on the poor prognosis in Lennox-Gastaut syndrome proceeded with West syndrome.