Propionic acidemia (PA) is an autosomal recessively inherited defect of propionyl-CoA carboxylase with an incidence of approximately 1:50 000. There are few reports on the occurrence of EEG findings and development of epilepsy in patients with PA. Retrospectively, the data of 17 patients with PA from one Italian and four Austrian centers were evaluated concerning EEG findings and the development of epilepsy. Nine patients showed a disturbance of background activity, as well as epileptiform discharges. All nine patients with pathological EEG discharges developed seizures compatible with the definition of symptomatic epilepsy. Five of these nine patients showed fever induced seizures at the beginning. Two of them suffered from symptomatic absence epilepsy. Six of the nine patients with seizures were treated with antiepileptic drugs (AED), which were tolerated without side-effects. Four patients showed photosensitivity, which so far has never been reported in PA. We hypothesize that patients with PA are prone to cortical dysfunction caused by one or several pathological metabolites - leading to changes in background and epileptiform activity with a high manifestation rate of clinical seizures.