We have isolated DNA clones encoding functional bradykinin receptors from human, rat, and mouse sources. Genomic bradykinin receptor clones have been isolated from mouse and human cosmid libraries and cDNA clones have been isolated from the human lung fibroblast cell line W138, from the neuroblastoma/glioma hybrid NG108-15, and from rat dorsal root ganglion cells. The receptor protein is encoded by an intronless region of the gene in both mouse and human. There is evidence of a splice acceptor site 8 bases upstream from the initiation codon in all three species. The function of the expressed receptor proteins from mouse, rat, and human was tested by electrophysiological assays after injection of cRNA into Xenopus laevis oocytes and also by binding assays with membranes from COS-7 cells transfected with cloned receptor-encoding DNA. The receptors from human and rat showed the pharmacological properties of B2 receptors in both expression systems when tested with a variety of bradykinin analogues, but receptors from mouse divided into two populations, one population with pharmacological properties of B1-like receptors and another, larger, population with properties of B2 receptors.