Chronic lymphoproliferative disorders are a heterogeneous group of diseases with a highly variable clinical course. In the past few years, important progress has been made in the classification, biology, and therapy of some of these disorders of which B-cell chronic lymphocytic leukemia is not only the most frequent but also the model for their study. Regarding classification, entities that may be confounded with chronic lymphocytic leukemia have been identified (eg, splenic lymphoma with villous lymphocytes, mantle-cell lymphoma in leukemic phase); these diseases should be known and clearly separated from chronic lymphocytic leukemia because their prognosis and treatment is different from that of chronic lymphocytic leukemia. On the other hand, the molecular basis of some of these diseases (eg, the overexpression of the Prad1/CCND1 gene in mantle-cell lymphomas, the relationship between bcl-2 and bax expression in chronic lymphocytic leukemia homeostasis, the role of p53 tumor suppressor gene mutations in chronic lymphocytic leukemia progression) are increasingly well known. Cytokines (eg, tumor necrosis factor-alpha or IL-2, IL-4, and IL-13) also contribute to the pathogenesis of lymphoproliferative disorders by either promoting cell growth or inhibiting apoptosis. In addition, new treatment possibilities (eg, purine analogues, hemopoietic progenitors transplants) are changing the treatment objectives in some of these diseases. Thus, symptoms' palliation is no longer the only realistic aim in the management of patients with chronic lymphoproliferative disorders, but sustained complete remissions and even cures can be achieved.