Chronic lymphocytic leukemia (CLL) is the most common form of adult leukemia in the Western world. It is often discovered on routine blood tests showing the presence of lymphocytosis. CLL has a variable course, with survival ranging from months to many years. In the past several years, discoveries of prognostic markers have helped predict the disease course. In terms of treatment, the emergence of purine analogs and monoclonal antibodies, such as rituximab (anti-CD20) and alemtuzumab (anti-CD52), has significantly changed the landscape of therapeutic options available for CLL.