Recent advances in neurodiagnostic technology, new insights into fundamental neuronal mechanisms of epilepsy, and rapid developments in molecular genetics have greatly improved our understanding of epileptic seizures and epileptic disorders since 1981, when the current International Classification of Epileptic Seizures was adopted, and since 1989, when the International Classification of Epilepsies, Epileptic Syndromes, and Related Disorders was adopted. Although both have been universally accepted and have proven to be of considerable clinical value, it has become clear that more is needed for specific applications of growing importance, such as presurgical evaluation, clinical pharmacology trials, and epidemiological studies. Therefore, an International League Against Epilepsy (ILAE) task force has evaluated the need for revising our current classification and terminology and has begun developing four specific documents. The first is a descriptive terminology for ictal phenomena, incorporating some of the concepts included in the preceding paper by Dr. Hans Lüders; however, this will be a glossary, not a classification. The second is a classification of epileptic seizures based on known or presumed pathophysiological and anatomic substrates, to replace the current classification, which is based entirely on phenomenology. The third is a classification of epileptic syndromes and epileptic diseases, adapted from the current Classification of Epilepsies, Epileptic Syndromes, and Related Disorders, which will take into account the fact that disorders with unique etiologies, such as a single gene, should be considered diseases, and which will be reorganized for maximum practical application to differential diagnosis. The fourth is a new classification of functional disability due to seizures or epilepsy, based on a new impairment classification for neurological disorders being developed by the World Health Organization. Working groups are currently in the process of developing each of these documents, and their chairs would benefit from any comments or suggestions from those who ultimately will be using these systems of classification and terminology.