Avian myeloblastosis virus (AMV), a source of reverse transcriptase for use in recombinant DNA work, is currently produced commercially from the plasma of leukemic chicks. Production involves inoculation of several hundred day-old chicks with AMV and harvest of virus-containing blood by heart puncture 7 to 10 days later. The research proposed will investigate the feasibility of commercial-scale production of AMV from cell cultures of chicken myeloblasts. Procedures for in vitro transformation of chicken macrophage lineage cells with AMV and the in vitro growth of the transformed cells on a small scale are well known. Large-scale culture of AMV-transformed myeloblasts has also been achieved, but with specially constructed apparatus. The present proposal discusses adaptation of recent advances in cell culture conditions and apparatus for large-scale cell culture to production of AMV. Successful development of the cell culture method will give a procedure that is both more economical and more humane than the present in vivo method.