- Purpose: Donor lymphocyte infusion (DLI) was used to reverse relapse after allogeneic bone marrow transplantation (BMT) in a patient with β-thalassemia major. Patients and Methods: The patient with unstable mixed chimerism after BMT was treated with graded increments of donor lymphocytes (10 5 T cells/kg to 5x10 7 T cells/kg) to displace residual hematopoietic host cells. Results: DLI resulted in complete donor-derived reconstitution of the hematopoietic compartment. The patient developed mild graft-versus-host disease (GVHD) that could be controlled by steroid treatment. Conclusions: This case report shows that DLI can effectively eradicate host stem cells in mixed chimeras after BMT in non-malignant hematopoietic diseases.