Background: When it comes to acute myeloid leukemia (AML), the large proportion of patients usually have relapses. Acute myeloid leukemia, Lymphoblastic lymphoma/leukemia, as well as Ewing sarcoma all have high CD99 expression. Objective: The aim of the current work was to assess CD99 expression frequency in patients with AML, and also to evaluate its association with different clinical and laboratory data. Patients and Methods: This comprehensive study included a total of 40 AML patients and 20 matched healthy subjects, attending at Departments of Clinical Pathology and Medical Oncology, Faculty of Medicine, Zagazig University Hospitals. Clinical and laboratory data were correlated with CD99 expression frequency in patients with AML in order to examine its usefulness as a predictive and prognostic factor. Results: Examination of CD99 expression in AML patients revealed that 80% of patients are CD99 positive, while (20%) are negative. Conclusion: CD99 expression in acute myeloid leukemia patients is of good prognostic value.