Immunocytochemical studies on the human embryo were made using antineuronal cell antibody and a panel of anti-extracellular matrix protein antibodies such as fibronectin, laminine, collagen type IV, and hyaluronic acid. All the enteric ganglia are shown to be from a single, vagal neural crest source, although the recent dual gradient migration theory of neural-crest-derived cells in the gut can be challenged. Neural-crest-derived cells first appear in the mesenchyme of the developing esophagus at 4 weeks, and then migrate down along the gut in a craniocaudal direction. The observed distribution of fibronectin and hyaluronic acid indicates the presence of these matrices providing a migration pathway for neural-crest-derived cells in the developing gut. The appearance of neural-crest-derived cells in the gut is always preceded by the appearance of these matrices. On the other hand, substrate or laminine and collagen type IV appears to promote outgrowth of neurites from settled neural-crest-derived cells and their maturation. The distribution of these matrices within the pathway seems consistent with their role in navigating the neural-crest-derived cells toward their final destination. Enteric neurogenesis is dependent on these matrices, and their alteration in early embryonal stage may be a significant factor in the pathogenesis of Hirschsprung's disease.