This chapter describes the immunocytochemical (ICC) localization of receptors in tissue sections and cells growing in culture. The protocol is illustrated using examples of how site-directed polyclonal antisera can be used to distinguish between subtypes of G protein-coupled receptors (GPCRs; endothelin ETA and ETB ), (1 ) in sections of human tissue or whole-body sections of mice, as well as mapping previously designated orphan receptors (oGPCR) recently paired with their cognate ligand illustrated by visualizing receptors for the peptide ghrelin (2 ). The methods are applicable to other receptor families.