Two cases with secondary generalized epilepsy whose epileptic attacks disappeared abruptly were reported. Permanent improvement was observed in case 1 with residual state of West syndrome, aged 4 years, after viral pneumonia, both epileptic attacks and epileptic discharges on EEG disappeared more than 3 years. Transient improvement was observed in case 2 with Lennox-Gastaut syndrome, aged 6 years, after an episode with insomnia, poor appetite and confusion for three days. After this episode epileptic attacks disappeared for 9 months and epileptic discharges on EEG were also markedly decreased. However, epileptic attacks relapsed following the reduction of phenytoin after 9 months. An effect resembling ketogenic diet therapy and a change of pharmacokinetics of antiepileptic drugs may be involved in the transient improvement of case 2. However, any effects involving an immunological effect and secretions of adreno-cortico-hormone following after stress may be not involved in the permanent improvement of case 1.