A 24-year-old man with acute myelomonocytic leukemia (AML-M4) who relapsed 6 months after an allogeneic BMT was treated with chemotherapy followed by donor leukocyte infusions (4.19 x 10(8) mononuclear cells/kg). The patient developed grade II acute GVHD that responded to therapy with CsA and prednisone. Chimerism was assessed by PCR amplification of the MCT 118 hypervariable region. Fourteen months after donor leukocyte infusions the patient remains in complete remission, without any morphologic and cytogenetic evidence of leukemia, and with a complete donor chimerism. This case shows that donor leukocyte infusions are an effective therapy for some acute myeloid leukemia patients who relapse after allogeneic BMT.