We describe two patients with acute myeloid leukemia successfully treated with anti-CD20 antibody for pure red cell aplasia (PRCA) following ABO-mismatched allogeneic hematopoietic stem cell transplantation (HSCT). PRCA following HSCT is associated with major ABO incompatibility between donor and recipient and is due to an inhibition of donor erythroid precursors by residual host isoagglutinins. The first patient developed PRCA resistant to several treatment options including donor-derived leukocyte infusions (DLI), high-dose erythropoietin (EPO), and rapid tapering of cyclosporin A (CsA). This patient also received anti-viral therapy as CMV and parvovirus B19 infections were regarded as additional causes of PRCA. Due to a loss of donor chimerism, he underwent second HSCT, but PRCA still persisted. He showed no evidence of graft-versus-host disease (GVHD). Finally he was administered anti-CD20 antibody (rituximab) at a dose of 150/m2 and PRCA resolved in a short period of time. The case was complicated by life-threatening pulmonary aspergillosis with septic shock, successfully treated with anti-fungal therapy. The second case concerns a patient, who revealed PRCA after major ABO-incompatible HSCT from his brother. Considering our experience with the previously described patient, he proceeded to rituximab at a dose of 150/m2 as first line treatment. We observed rapid recovery from PRCA without any side effects. We conclude that rituximab seems to be a promising therapeutic option in patients with PRCA after ABO-mismatched HSCT, in whom conventional treatment fails.