This article reviews the pathogenesis and pathology of the most common focal malformations of cortical development in association with epilepsy. The classification of these disorders is reviewed in the context of new developments in the areas of diagnosis and genetics. The major pathological substrates and the possible mechanisms of these malformations are discussed. The possible mechanisms of epileptogenesis in the context of focal malformations are complex and poorly understood at present. Advances in this area promise to enhance our understanding of the basic mechanisms of epilepsy.