An X-linked severe combined immunodeficient (SCID) patient received a nonirradiated erythrocyte transfusion and developed transfusion-associated graft-versus-host disease (TAGVHD), which was controllable with high-dose corticosteroids. Haplo-identical SCT was performed, after a myeloablative conditioning regimen. At day +26, he developed GVHD. Chimerism studies revealed DNA of the erythrocyte transfusion donor (ETD) and recipient only. Because of early nonengraftment and the presence of alloreactive T cells of ETD origin, the patient was treated with an immunosuppressive conditioning regimen followed by a second SCT from the same donor. While tapering immunosuppression, he again developed mild GVHD, and DNA of ETD and bone marrow donor origin were both present. On cyclosporin, the ETD-DNA signal finally disappeared. High-resolution HLA typing revealed haplo-identity between BMD, ETD and the patient, which might have contributed to the relative mild course of the TAGVHD.