 Although allogeneic stem cell transplantation is curative in CML, evidence of the BCR-ABL oncogene at low levels is still found in long-term follow-up of survivors. Such low levels of BCR-ABL post-transplant, which do not fulfill criteria for molecular relapse are monitored regularly and considered to be suppressed by the GVL effect. Treatment with donor lymphocyte infusions is only instituted when quantifiable BCR-ABL transcript levels rise steadily, indicative of a true molecular relapse. 