Over the past decade, genetic analyses have yielded a more molecular view of neuronal migration and its role in central nervous system development. We now realize that many of the molecular mechanisms that guide migrations in invertebrates are recapitulated in the vertebrate nervous system. These mechanisms guide dorsoventral and anterior-posterior migrations and merge with radial migratory pathways that are prominent in the development of the mammalian cortex. This review discusses the choreography of these different migratory mechanisms within the context of genetic approaches that have defined their molecular mechanisms.