Background: Acute myeloid leukemia (AML) is a heterogeneous hematopoietic tissue neoplasm. Response assessment is evaluated by undergoing bone marrow examination on day 28 from initiation of therapy. Patients and methods: 60 newly diagnosed AML cases were. Blast percentage obtained in bone marrow biopsy using CD34 immunohistochemistry on day 28 after induction chemotherapy compared with that obtained in bone marrow aspirate smears and flow cytometry. In addition, counting of immature CD34 positive clusters and evaluation of bone marrow microvessel density (MVD) and relating them to prognosis were performed. Results: Blast percentage in bone marrow aspiration smears and CD34 immunohistochemistry was discordant in 21.7% with a statistically significant difference. While, discordance between flow cytometry and CD34 immunohistochemistry was 13.3 % with no statistically significant difference. upstaging by CD 34 immunohistochemistry had a statistically significant shorter OS, DFS and EFS. In addition, immature CD34 clusters found to have a significant effect on remission rate and MVD suggested to be important in predicting relapse. Conclusion: Assessment of response to chemptherapy using CD34 immunohistochemistry provides more accurate method for counting blast cells with subsequent reinduction therapy decision. In addition, immature clusters and MVD could be considered as prognostic factors of AML patients. Keywords: CD34, Acute myeloid leukemia, Immunohistochemistry, Bone marrow biopsy, Survival