An antibody directed at the carboxy tail of the cholecystokinin-1 receptor (CCK1R) was characterized by ELISA and Western blotting. Immunohistochemistry established that CCK1R-like immunoreactivity (CCK1R-LI) was widely and topographically distributed through the neuroaxis, appearing relatively higher in rhi- and diencephalon, and intense in both neuronal somata (cytoplasmic) and processes. CCK1R-LI was found in new loci, but also in areas previously identified by receptor autoradiography, electrophysiology and in situ hybridization of CCK1R mRNA. The widespread distribution of CCK1R has implications for the functional roles of these receptors in brain. The high titre and low background seen with this new antiserum makes it of great value for cell and tissue research.