The genes encoding the two kinin receptors, B1 and B2, are closely linked on the same chromosome in human, mouse, and rat. In this article, we present the organisation of the B B2 locus in these mammals. This organisation was obtained by comparing the kinin receptor mRNA sequences of man and mouse with the sequence of chromosomes 14 and 12, respectively. We found that the two genes are located in tandem orientation, separated by only 7.8 kb in mice and 12 kb in humans. The distance of the two genes on rat chromosome 6 was determined by long-range PCR to be 9.5 kb. The organisation of the two genes encoding the kinin receptors is similar in the three species, except that the human B1 gene harbors an additional exon, which may originate from the insertion of an Alu repetitive sequence during evolution. Moreover, the human and rat, but not the murine, B2 genes carry an alternatively spliced exon between exons 2 and 3, termed exon 2b.