In avian embryos, trunk neural crest migrate segmentally through the somites entering the rostral but not caudal somitic sclerotome. Inhibitory molecules in the caudal somite could prohibit entry of neural crest caudally, and thus restrict cell migration to rostral somite territories. Two sets of cues, peanut agglutinin (PNA) binding glycoproteins and members of the Eph family of receptor tyrosine kinases (RTKs) and their ligands appear to play this role in segmenting cell migration. Addition of exogenous PNA to neural crest migrating in trunk explants disrupts the normal segmental pattern of migration: neural crest travel in rostral and caudal regions of the somites. Members of the Eph family display the correct spatiotemporal localization to influence neural crest migration: the RTK EphB3 is expressed by neural crest, whereas the transmembrane ligand ephrin-B1 is expressed by caudal sclerotomal cells. Exogenous ephrin-B1 added to nerual crest migrating in trunk explants also specifically disrupts the segmental organization of neural crest migration. Isolated neural crest avoid lanes containing ephrin-B1 in vitro; this avoidance is abolished by addition of soluble ligand. Time-lapse imaging reveals that neural crest exhibit a typical collapse response followed by process retraction upon encountering ligand. The results of these studies implicate PNA-binding glycoproteins and Eph family members in sculpting the migratory patterns of neural precursors in the peripheral nervous system.