The patient was a 47-year-old man who was diagnosed in 1989 as having chronic myelogenous leukemia (CML). He had been treated with interferon-alpha (IFN-alpha) and hydroxyurea. In August 1999, he was admitted to our hospital for examination of severe anemia and increased platelet count. On admission, his hemoglobin level was 6.3 g/dl, reticulocyte count was 0.7%, WBC count was 5,100/microliter, and platelet count was 57.3 x 10(4)/microliter. Bone marrow aspiration showed myeloid hyperplasia and near absence of erythroblasts. Bone marrow karyotype analysis showed a Ph chromosome with additional abnormalities. Pure red cell aplasia (PRCA) with accelerated-phase CML was considered. The IFN-alpha therapy was discontinued. Hydroxyurea at an increased dosage was effective in controlling the CML. In contrast, administration of cyclosporin A was not effective for the PRCA. The patient's condition was later complicated by acute hepatitis C virus infection. The IFN-alpha was restarted to control the CML and hepatitis. The patient remained erythroblastopenic and transfusion-dependent for more than 2 years. Association of CML and PRCA is rare. We discuss the mechanisms underlying PRCA occurring during the course of CML.