Acute myelogenous leukemia (M2) with translocation of 8;21. Was diagnosed in 61-year-old man. He was successfully treated and obtained complete remission. After consolidation therapy, myeloid suppression and maturation arrest at the myelocyte level were recognized. Following intensive chemotherapy, he received rhG-CSF-mobilized peripheral blood stem cell transplantation (PBSCT) from an identical twin because he had life threatening infectious events and protracted myelosuppression. Transplantation of 2.5 x 10(6)/kg CD34+ cells resulted in a rapid normal tri-lineage hematologic reconstitution. Syngeneic PBSCT appears to be a substitute for syngeneic bone marrow transplantation in certain situations.