A 54-year-old man was admitted with fatigue. The peripheral blood count showed leukocytosis (9, 600/microliters), including 76% granular lymphocytes (GLs), which expressed CD2, 3, 8, 16 and HLA-DR, and anemia (hemoglobin 8.1 g/dl). He was diagnosed as having T cell type-granular lymphocyte proliferative disorder with anemia. Bone marrow examination revealed the involvement of 4.6% of GL and erythroblastopenia. A clonogenic assay of bone marrow cells revealed the decrease in erythroid colony formation in both CFU-E and BFU-E, but the number of erythroid colonies increased when CD8-positive cells were depleted from bone marrow cells and the number of erythroid colonies decreased again when CD8-positive GLs were added. The supernatant of cultured CD8-positive GLs had no inhibitory effect on CFU-E and BFU-E colony formation. These suggested that CD8-positive GLs suppressed the erythroid colony formation in this case. Treatment with 6,000 U/body of recombinant human erythropoietin (rh-Epo) subcutaneously three times a week was started and increased dose of 12,000 U/body of rh-Epo led to an increase in the hemoglobin level to 10.5 g/dl two months later. He has been treated with rh-Epo only.