Chronic lymphocytic leukemia (CLL) is a common adult leukemia characterized by the extensive accumulation of monoclonal, relatively mature , positives of cluster of differentiation antigen 5 and cluster of differentiation antigen 23 B lymphocytes in lymphoid organs, bone marrow, and peripheral blood. CLL cells accumulate because of defective apoptosis, which extends survival. CLL is a heterogeneous disease. Chemoimmunotherapy is the standard front-line approach for patients younger than 65 years with CLL, with the combination of fludarabine, cyclophosphamide, and rituximab used most commonly. Some CLL patients do not respond well to routine chemoimmunotherapy. Despite recent advances in the treatment of CLL by use of modern chemoimmunotherapy, the disease remains incurable for most patients with the exception of those who have the option of an allogeneic transplantation. However, treatments with chemoimmunotherapy are associated with significant toxicities and sustained immunosuppression, and the rates of myelosuppression and infection are high. Such complications are more frequent and more severe in patients older than 65 years because of reduced marrow reserve, and presence of comorbidities. Because CLL is a disease of the elderly, identifying effective therapies with better toxicity profiles is thus a high priority, and targeted therapies may allow attainment of this goal.