Mohammed Shanshal, MD, and Rami Y. Haddad, MD, FACP hronic lymphocytic leukemia [chronic lymphoid leukemia (CLL)] is a onoclonal disorder characterized by a progressive accumulation of unctionally incompetent lymphocytes. The most characteristic feature of LL is a peripheral blood absolute lymphocytosis ( 5.0 10/L, but sually 15.0 10/L and sometimes 100.0 10/L). It is the most common form of leukemia (Table 1) found in adults in estern countries, accounting for approximately 30% of all leukemias in he USA. The proportion of cases diagnosed with the early stages of the isease [Rai Stage 0 (Table 2)] has risen from 10% to 50%, probably ecause of earlier diagnosis (routine automated blood counts). This xpansion is the result of prolonged cell survival, despite a varied cell urnover. The affected lymphocytes are of B-cell lineage in 95% of cases that arry CD5, and the remaining cases involve T lymphocytes, representing distinct disorder. Onset is insidious, and it is not unusual for CLL to be discovered ncidentally after a blood cell count is performed for another reason. nlarged lymph nodes are the most common presenting symptom, but atients may present with a wide range of symptoms and signs. hemotherapy is not needed in CLL until patients become symptomtic or display evidence of rapid progression of disease. A variety of hemotherapy regimens are used in CLL. These may include nucleoide analogues, alkylating agents, and biologics, often in combination. llogeneic stem cell transplantation is the only known curative herapy.