The localization and co-localization of pituitary adenylate cyclase activating polypeptides (PACAPs) and vasoactive intestinal polypeptide (VIP) in the enteric nerve plexus of the guinea pig jejunum were immunohistochemically compared by the peroxidase anti-peroxidase (PAP) method using region-specific antisera against PACAP38, PACAP27 and VIP, respectively. Immunoreactive nerve elements were demonstrated in the ganglia of both myenteric and submucous plexi in the guinea pig jejunum. Numerous immunoreactive nerve cell bodies were localized in the myenteric ganglia, while nerve cell bodies in the submucous ganglia were only slightly immunopositive. Immunoreactive nerve terminal varicosities occurred in both myenteric and submucous ganglia. Additionally, PACAPs-immunoreactive nerve cell bodies were also immunopositive with VIP. Thus, both PACAP38 and PACAP27, as well as VIP, are co-localized in the cell bodies of guinea pig jejunum.