Of 229 consecutive patients receiving allogeneic blood or bone marrow stem cell transplants for acute myeloid leukemia, chronic myeloid leukemia, or myelodysplastic syndrome between 1974 and 1996, 52 patients relapsed. The original tumor recurred as granulocytic sarcoma (chloroma) in three patients (1.3%). Chloroma was found in the ovary in two patients and in the central nervous system in one patient. None of these three patients had experienced > or = grade II acute or more than limited chronic graft-versus-host disease. The intervals between transplantation and recurrence with chloroma were 2, 6, and 13 years. Two patients received a second transplant, and all three died of treatment sequelae.