We have previously shown that depletion of CD4+CD25+FoxP3+ regulatory T cells (Treg) enhances the alloreactivity of T lymphocytes, as attested by an accelerated GVHD after allogeneic hematopoietic stem cell transplantation (HSCT) in mice. We thus propose a clinical trial to test whether Treg-depleted donor lymphocytes infusion (dDLI) could induce an improved graft-versus-tumor (GVT) effect in patients refractory to standard DLI (stdDLI) for treatment of relapse after HSCT.