Summary Objectives To describe the EEG characteristics of patients with Unverricht-Lundborg disease (ULD) and their changes during the long-term evolution of the disease. Methods A retrospective study including all patients with ULD confirmed by molecular biology and more than 15 years’ duration of disease progression at the time of inclusion. EEGs were recorded at inclusion, 2 years and 5 years of follow-up. Patients who discontinued treatment during follow-up had an EEG monitoring 1 year after reintroduction of therapy. Results Forty-seven EEGs were performed in 17 patients. The mean age at onset was 12.0 ± 5.5 years. The mean duration of follow-up was 26.5 ± 6.9 years. The average background rhythm was 8.2 c/s, and was normal in 30 EEGs (64%), slow in 17 (36%) and disorganized in 11 (23%). Epileptic abnormalities were found in 22 EEGs (47%). Myoclonic jerks were found in 13 EEGs (28%). After re-adaptation of antiepileptic medication in patients who had previously stopped treatment, control EEG showed a normal background rhythm with no epileptic abnormalities throughout the monitoring period. Conclusion This study shows that the progressive disappearance of EEG abnormalities is rather due to antiepileptic treatment than a gradual spontaneous tendency to decrease over time.