Chronic lymphoid leukemia (CLL), is the most common type of leukemia (a type of cancer of the white blood cells) in adults representing 25%-30% of all leukemias, CLL is a disease of adults. Most (>75%) people newly diagnosed with CLL are over the age of 50, and the majority are men, The leukemia is characterized by a clonal expansion of long-lived mature-appearing B lymphocytes that co-express the CD5, CD19, and CD23 surface antigens.CD39 (ectonucleotidase, NTDPase1) is an ADPase found on the surface of endothelial cells, normal lymphocytes and other leukocytes, Its principal function on the endothelial cell surface is to decrease platelet activation and recruitment by metabolizing platelet-released adenosine diphosphate (ADP). In leukocytes the enzyme has a variety of other direct or indirect effects as well, including modulation of cytokine expression and the inflammatory response. The aim of this study to review the role CD39 in patients with chronic lymphocytic leukemia and correlate it with the severity of the disease. A total of 5 papers were obtained using the mentioned keywords in the research of all internet-based databases. The total number of cases in all of the studies was 716 cases.The mean age was recorded in 5 papers was 64.7 years. There are different method of detection of CD39 in different studies such as flow cytometry and immunohistochimistry .