Lampreys belong to the most ancient branch of living vertebrates. They have one of the simplest nervous systems among vertebrates, thus retaining many ancient traits. Our main goal is to study the organization and development of the lamprey brain and spinal cord, from an evolutionary point of view. We use tract tracing, immunhistochemistry and in situ hybridization techniques to identify specific nuclei, regions and pathways in the central nervous system, and compare them with those of higher vertebrates. The results are considered according to the segmentary model of vertebrate brain organization.