Allogeneic stem cell transplantation takes advantage of donor immunocompetent T lymphocytes to have an antimalignancy or antileukaemic effect, however which is associated with graft versus host effect generally. The allogeneic transplantations of peripheral blood stem cells are overbearing in the last ten years, which induce faster engraftment and fewer relapses of disease, while acute and chronic graft versus host disease are more frequent. There are new ways that significantly increase the indication of allogeneic stem cell transplantation: 1. transplantation with reduced intensity conditioning to decrease toxicity chemo or chemoradiotherapy, when the donor T lymphocytes have the major antimalignancy effect; 2. donor leukocytes infusion to intensification of antimalignancy effect. Monoclonal antibody Campath 1 was developed for clearence T lymphocytes from donor graft. On the present time there is available the humanised anti-CD 52 antibody alemtuzumab, which have the rat variable part of immunoglobuline and other parts are human. The usage of alemtuzumab during alogeneic stem cell transplantation drop intensity of graft versus host disease, while relapses and infections are more often. There are not a lot of data about results of combination alemtuzumab with chemo and chemoradiotherapy. The way of alemtuzumab is important for its effect: 1. intravenous administration has antimalignant effect and immunosupressive effect to host cells and might make depletion of T lymphocytes in the graft; 2. administration into the bag with donor graft makes only depletion of T lymphocytes. Alemtuzumab is useful for treatment of developed graft versus host disease, but there are a few data so far.

        Key words: allogeneic stem cell transplantation, graft versus host disease, immunosuppression, Campath, alemtuzumab