Recent genetic insight into the mechanisms of human brain malformation have allowed one to consider a classification of these disorders by the genetic disruption. In this article an attempt is made to classify human cortical dysplasias by the known genetic disruptions or insults that lead to them. The discussion of malformation is within the context of the embryologic processes that have thought to have gone awry. Human disorders of segmentation, cell proliferation, telencephalic cleavage, differentiation, and neuronal migration are discussed. As this is a rapidly changing area, the reader is encouraged to check online databases for updates on the genetic insights that have been gained since the publication of this article.