Abstract: Recombinant DNA molecules in which an avian retroviral long terminal repeat (LTR) has been ligated to the bovine growth hormone gene are described herein. The retroviral LTR was derived from a plasmid clone of a Schmidt Rupin strain of Rous Sarcoma Virus while the bovine growth hormone (BGH) gene was derived from a lambda-bacteriophage genomic library. Using a transient eucaryotic expression assay system, the plasmid constructs were screened for their ability to direct expression and secretion of bovine growth hormone. These constructs were co-transformed into a mammalian cell (mouse) culture in order to obtain a stable cell culture secreting large amounts of bovine growth hormone.