In general, epileptic seizures become more serious following infections. However, transient and permanent improvement of epileptic seizures has been observed following acute viral infections, without a recent change in anti-epileptic therapy. Questionnaires were sent to 73 institutions, throughout Japan, where pediatric neurologists care for children with epilepsy to characterize this phenomenon through clinician survey. Completed surveys were received from 11 institutions, and 21 cases were selected for the study. The age of the patients were 6 months to 17 years. The West syndrome or epilepsy subsequent to West syndrome cases were 16 out of 21. Two cases of symptomatic generalized epilepsy and one case each of symptomatic partial epilepsy, continuous spike-waves of slow sleep and severe myoclonic epilepsy in infancy were also reported. These seizures disappeared within 2 weeks subsequent to viral infections such as, exanthema subitum, rotavirus colitis, measles and mumps. The disappearance of intractable epileptic seizures following acute viral infections might be related to the inflammatory processes or the increased levels of antibodies after viral infections.