Ephrins are cell surface associated ligands for Eph receptor tyrosine kinases and are implicated in repulsive axon guidance, cell migration, topographic mapping and angiogenesis. During the past year, Eph receptors have been shown to associate with glutamate receptors in excitatory neurons, suggesting a role in synapse formation or function. Moreover, ephrin/Eph signaling appears to regulate neural stem cell proliferation and migration in adult mouse brains. The mode of action of ephrin/Ephs has been expanded from repulsion to adhesion and from cell surface attachment to regulated cleavage.