Both the investigation of the enteric nervous system and the diagnosis of its pathological changes require reliable staining methods. In order to assess the potential of protein gene product (PGP) 9.5 as a marker for the enteric nervous system, we examined its immunoreaction in whole-mount preparations of the guinea pig and porcine small intestine, using a rabbit polyclonal antiserum.The immunohistochemical technique reveals the fundamental architectural features of the ganglionic and aganglionic plexuses. Furthermore, it enables a reproducible and differentiated visualization of the enteric nerve cells to be made, so that the various nerve cell types can be morphologically identified.