Donor lymphocyte infusion has become established as a salvage therapy for patients with hematological disorders relapsing after allogeneic bone marrow transplantation (BMT). The role of donor lymphocyte infusion for patients with myelodysplastic syndrome (MDS) remains to be established. Between July 1993 and October 2001, 14 patients with MDS relapsing after allogeneic BMT received DLI as salvage therapy. At the time of BMT, one patient had RA, nine had RAEB, of whom three were in CR after induction-type chemotherapy, two had RAEB-T, one had CMML and one had AML. Donors were HLA-matched siblings (n=12), HLA-matched other relative (n=1) and unrelated (n=1). At the time of relapse, the median marrow blast count was 9%. The median CD3+ cell dose administered was 6.3 x 10(7)/kg. With a median follow-up of 49 months, six patients were alive, of whom two were in CR after DLI alone and remained disease-free, two were in CR after a second BMT and two had active disease. Eight patients died of disease progression. Although DLI alone seems to be effective in a small number of patients with MDS, other treatment strategies, including prior debulking chemotherapy, deserve investigation.