Recombinant human erythropoietin (rHu EPO) has been reported to accelerate early erythroid reconstitution after bone marrow transplantation (BMT). We conducted a pilot study on rHu EPO for late-onset anemia in 9 patients after allogeneic BMT. The patients achieved initial erythropoietic recovery (hemoglobin (Hb) range 9.1-13.4, mean 10.8 g/dl), but then developed transplant-related anemia (Hb range 6.3-9.7, mean 8.2 g/dl) more than 50 days after BMT. This type of anemia was related to graft-versus-host disease (GVHD), cytomegalovirus infection, and/or impaired EPO secretion. The patients received 3,000 or 12,000 U of rHu EPO subcutaneously three or seven times weekly. Hb levels increased by more than 2 g/dl in 6 of the 9 patients, but were unchanged in the 3 patients with severe GVHD. These findings suggest that in some cases rHu EPO is effective for the treatment of late-onset anemia after BMT.