Progress in experimental bone marrow transplantation in dogs has provided for the direct transfer of research data to the clinical setting and the therapeutic application of marrow grafting to a variety of human diseases. Animal models of total body irradiation, engraftment and graft-versus-host disease are still needed to solve the existing clinical problems of marrow transplantation. Therefore, work in various canine model systems continues to be of interest. Pet dogs with spontaneously occurring lymphomas are used to study the clinical parameters necessary for applying the technique of transplanting their own marrow (autologous), in conjunction with high dose radiation and/or chemotherapy, to human patients with cancer. A major consideration in the successful transplantation of donor bone marrow (allogeneic) is overcoming histocompatibility barriers to assure engraftment and the prevention of graft-versus-host disease, a major limiting aspect of clinical marrow transplantation. Chemicals, radiation, radiotherapeutic techniques, antisera and monoclonal antibodies have been and continue to be developed in laboratory bred dogs. These approaches suppress the immune system either nonspecifically by ablation of immune reactive tissue, or specifically by affecting certain types of immune reactive cells. Parameters such as clinical effectiveness (engraftment or prevention of graft-versus-host disease), immune reconstitution and undesirable side affects in long-term survivors are all used to determine whether new technology can be transferred from preclinical canine studies to human bone marrow transplantation protocols.