This report concerns a case of long-lasting pure red cell aplasia (PRCA) with a duration of 178 days after major ABO-incompatible allogeneic peripheral blood stem cell transplantation (PBSCT). The patient needed red blood cell transfusion every week from day 54 following PBSCT. He showed no evidence of GVHD and the dose of cyclosporin A (CsA) was reduced rapidly from day 123, followed by the development of chronic GVHD around day 145. The patient no longer needed transfusions from day 167, the reticulocyte count began to increase on day 179, and antidonor isohemagglutinin titers became undetectable. Chronic GVHD induced by tapering of CsA thus appeared to be related to improvement in PRCA.