Teneurin (Ten-m/Odz) molecules represent a highly conserved family of four type II transmembrane proteins in vertebrates (Ten-m1-4), which exist as homodimers and undergo homophilic interactions. Each is expressed in distinct, and often interconnected, areas of the developing nervous system. Different Ten-ms have complementary expression patterns. In vitro and in vivo studies support roles for teneurins in promoting neurite outgrowth and cell adhesion. Furthermore, the intracellular domains of at least two teneurins can undergo proteolytic cleavage and translocate to the nucleus where they regulate transcriptional activity. Recent in vivo studies show that teneurins play important roles in regulating connectivity in the nervous system. Knockdown in C. elegans resulted in abnormal axon guidance and cell migration, while targeted deletion of Ten-m3 in mice revealed it is required for the guidance of retinal axons and generation of visual topography. It is likely that all teneurins play important roles during neural development.