Using monoclonal antibody 171B5 against synaptic vesicle proteins, neuromuscular junctions and synapses in the muscle layers of the bowel affected by hypoganglionosis were labeled and their distribution analysed. In the hypoganglionic bowel, there were less synapses in the myenteric plexus and few neuromuscular junctions compared to normal bowels. The bowel dysmotility of the patient with hypoganglionosis appears to be due to inadequate innervation between ganglion cells and smooth muscle cells.