The human and mouse genes for the neuropeptide Y4 receptor have been isolated, sequenced, and shown to contain no introns within the coding region of the gene. Nonisotopic in situ hybridization and interspecific mouse backcross mapping have localized the genes to human chromosome 10q11.2 and mouse chromosome 14. Five nucleotide variants, which do not alter the protein sequence, have been identified within the coding region of the human receptor gene. The human Y4 subtype is most closely related to the Y1-receptor subtype (42%), suggesting that it evolved from an ancestral Y1-like receptor via an RNA-mediated transpositional event.