Primary pure red cell aplasia (PRCA) was diagnosed in two male patients, 65 and 69 years old respectively. In both, surface markers of peripheral blood nuclear cells revealed the presence of TCRalphabeta+ phenotype. Clonality of T cells was confirmed by the polymerase chain reaction in both patients, in whom, prednisone at a dose of 1 mg/kg/day improved the anemia and lower doses caused its renewal, resulting in the reappearance of the patient's transfusion requirement. On the other hand, the anemia seems to have been treated permanently (second case) with horse antithymocyte globulin (ATG) (20 mg/kg/day 1 to 8 +) since his hemoglobin was about 15 g/dl at the time of writing. In the first patient, the hemoglobin level was 10.5 g/dl one month after the administration of ATG (15 mg/kg/ d 1 to 5 +), but unfortunately, the patient died because of a massive gastrointestinal bleeding on the fortieth day following this treatment. We, therefore, suggest that, patients with acquired primary PRCA should be screened to detect the presence of a T-cell clone and recommend that, treatment should start earlier with ATG, if the PRCA is due to a T-cell clonal disorder.