In this study we investigated the significance of CD71 (transferrin receptor 1, TfR-1) as a flow cytometric marker in the diagnosis of acute leukemia (AL). A total of 105 patients with AL were enrolled. Poorly differentiated acute myeloid leukemias (AMLs) (including minimally differentiated AML, AML without maturation, AML with maturation, acute myelomonocytic leukemia) tended to express high levels of CD71 on leukemic cells, while partially differentiated AML (including acute promyelocytic leukemia and acute monocytic leukemia) often expressed low levels of CD71 on leukemic cells (p < 0.05, compared to poorly differentiated AML). B-cell acute lymphoblastic leukemia (B-ALL) expressed low levels of CD71 on leukemic cells, significantly lower than AML, mixed phenotype acute leukemia (MPAL) and normal bone marrow blasts (p < 0.05). In the seven cases of acute erythroid leukemia (AEL), leukemic cells rarely expressed CD71, with the mean CD71 expression level significantly lower than that of acute megakaryocytic leukemia (p < 0.05), and also lower than that of poorly differentiated AML and normal blasts but without statistical significance. CD71 may not be a specific marker for AEL leukemic cells. During the process from myeloid dysplasia to apparent leukemic cells, both CD71 and CD34 gradually increased. Consequently, the presence of leukemic cell subsets with variable levels of CD71 and CD34 may be useful for understanding the dynamic processes involved in the clonal development seen in leukemias.