Epilepsy is a chronic disorder of the brain characterized by recurrent unprovoked seizures. A seizure is a sudden change in behavior that is accompanied by electrical discharges in the brain. Many patients presenting with a first-ever seizure are surprised to find that it is a very common event. A reversible or avoidable seizure precipitant, such as alcohol, argues against underlying epilepsy and therefore against treatment with medication. This chapter discusses the epidemiology, etiology, and classification of epilepsy and provides detailed descriptions of neonatal syndromes, syndromes of infancy and early childhood, and syndromes of late childhood and adolescence. The pathophysiology, diagnosis, and differential diagnosis are described, as are syncope, migraine, and psychogenic nonepileptic seizures. Two case histories are provided, as are sections on treatment (polytherapy, brand-name versus generic drugs, surgery, stimulation therapy, dietary treatments), complications of epilepsy and related disorders, prognosis, and quality measures. Special topics discussed are women?s issues and the elderly. Figures illustrate a left midtemporal epileptic discharge, wave activity during drowsiness, cortical dysplasias, convulsive syncope, rhythmic theta activity, right hippocamal sclerosis, and right temporal hypometabolism. Tables describe international classifications of epileptic seizures and of epilepsies, epilepsy syndromes and related seizure disorders, differential diagnosis of seizure, differentiating epileptic versus nonepileptic seizures, antiepileptic drugs, status epilepticus protocol for treatment, when to consider referral to a specialist, and quality measures in epilepsy. This review contains 7 figures, 17 tables and 38 references Keywords: Seizures, focal (partial)seizure, generalized seizures, Myoclonic seizures, Atonic seizures, Concurrent electromyographyTonic-clonic (grand mal) seizures