In retrovirus research, the generation of an infectious molecular clone is a landmark event, opening up new avenues of research using the cloned virus. A full-length proviral plasmid clone of the human T-cell leukemia virus (HTLV) makes possible reproducible viral genetic studies. However, the growth of full-length infectious HTLV proviral plasmid clones in bacteria, their manipulation using molecular techniques, and further characterization of replication capacity and other biological properties are not trivial. This chapter describes successful methods used for the preparation and manipulation of the full-length HTLV-2 proviral plasmid clone pH6neo. The plasmid-borne full-length clone of HTLV-2 permits the study of the interactions and contributions of viral proteins in viral replication and cellular transformation in vitro and in animal models in vivo. These types of studies have provided and will continue to provide critical insight into understanding the virus-host interactions and ultimately the contribution of viral genes and elements to the pathogenesis of HTLV.