Although inborn errors of metabolism are rarely found to be the cause of epilepsy, seizures are a frequent symptom in metabolic disorders. In a few of these, epilepsy responds to specific treatment by diet or supplementation. However, in most, no such treatment is available and conventional antiepileptic drugs must be used, often with no great success. However, because uncontrolled epilepsy will hamper development and may even lead to further cerebral damage, treatment is necessary. Seizure types are rarely specific for a particular metabolic disorder, nor are EEG findings. Other symptoms and findings must be taken into account in order to achieve a diagnosis and, in some cases, specific management. We review the main characteristics of epilepsy due to inborn errors of energy metabolism, to disturbed neuronal function due to accumulation of storage products, to toxic effects and to disturbed neurotransmitter systems. We also discuss vitamin-responsive epilepsies and a number of other metabolic disorders focusing on possible pathogenetic mechanisms and their implication for diagnosis and treatment.