The monoclonal antibody HNK-1 was used to identify neural crest cells in serial sections of avian embryos to provide a detailed description of the distribution of trunk neural crest cells. The results indicate the presence of three migratory routes in the trunk: (1) a ventral pathway through the anterior sclerotome; (2) a ventral pathway between the neural tube and the posterior sclerotome; and (3) a dorsolateral pathway between the somites and ectoderm. Neural crest cells were first seen entering the anterior half of the sclerotome at about the time the somite begins to dissociate to form the dermomyotome and sclerotome, approximately 5-10 somites rostral to the most recently formed somite. In contrast, neural crest cells were never observed in the posterior sclerotome or in the perinotochordal space. The distribution of neural crest cells was compared with that of injected latex beads which were previously found to translocate along the ventral trunk neural crest pathway (Bronner-Fraser, Dev. Biol. 91, 130, 1982). During the early stages of neural crest migration, injected latex beads were found to extensively colocalize with cells stained by the HNK-1 antibody. Injected latex beads (78%) were found immediately adjacent to HNK-1 positive cells and another 11% were within one cell diameter. The results suggest that latex beads injected into the trunk somites are deposited onto a normal pathway of neural crest migration.