Monoclonal antibodies (MAb) directed against neuron-specific epitopes are valuable tools in the diagnosis of congenital and acquired enteric nervous system anomalies. MAb raised against cytoskeleton proteins (neurofilaments) revealed a characteristic staining pattern in patients with various motility disorders of the gut. Application of MAb in the study of the development of the enteric nervous system in the chicken embryo provided new insights into the fate of migrating neural crest cells. The relationship between mesenchymal target cells in the gut and proliferating neural crest cells was studied by means of MAb raised against cell surface markers (HNK-1) in combination with characterization of the microenvironment using monoclonal antibodies raised against cell adhesion molecules (N-CAM).