We report an unexplained anemia that persisted for 4 months in a renal transplant patient who was receiving immunosuppression therapy that included prednisolone, tacrolimus, and azathioprine. A bone marrow biopsy demonstrated pure erythroid hypoplasia and occasional giant pronormoblasts with intranuclear inclusions, characteristic of a parvovirus B19 infection. Both the serum and bone marrow cells were positive for a parvovirus B19 DNA polymerase chain reaction. The anemia resolved 6 weeks after the administration of IV immunoglobuln. But, 4 months later, refractory anemia developed and persisted despite treatment with IV immunoglobulin. However, the patient showed rapid improvement after tacrolimus was switched to cyclosporin A. A parvovirus B19 infection should be included in the differential diagnosis of renal transplant recipients who present with an anemia associated with low reticulocytes; and clinicians should be awared that tacrolimus may impair the clearance of a parvovirus B19 infection.