Studying the functional properties of chimeric adrenergic receptors has helped to define the domains responsible for ligand binding specificity and coupling to G-proteins. Of the methods available for the construction of chimeric genes, the linker-adapter approach is the simplest and often the most rapid technique; however, in practice this method is not always feasible. The advent of polymerase chain reaction technique made possible rapid construction of chimeric genes by splicing at virtually any site. The functional properties of chimeric proteins can be studied by expressing the chimeric genes in Xenopus oocytes or in mammalian cell lines such as COS and Raji cells. Mammalian cells are also useful for immunocytochemical localization studies because major incompatibility among the structural domains from the two parent receptors often results in misfolding and retention of the chimeric protein in the endoplasmic reticulum.