[en] Allogeneic hematopoietic stem cell transplantation (HSCT) is used for the treatment of selected haematological malignancies. Its curative potential is based on two different mechanisms, i.e. the conditioning regimen and the graft-versus-host immunologic reactions. However, because of its toxicity, it is restricted to younger and fitter patients. These observations led several groups to set up new (less toxic) transplant protocols. These transplants are called nonmyeloablative HSCT or minitransplants. These are feasible with a relatively low transplant-related mortality even in patients up to 70 years. In addition, strong anti-tumor responses are observed in several haematological malignancies.