In the last two decades, important advances have been made in the biology, natural history, and prognosis of B-cell chronic lymphocytic leukaemia (CLL). In addition, treatment possibilities for patients with CLL have changed as a result of the identification of prognostic factors for survival and the availability of new drugs and treatment strategies. Patients in the early clinical stages (Binet A, Rai 0) with stable disease have a probability of long survival and should not be treated unless the disease progresses. In contrast, most patients with poor prognostic features, such as an advanced clinical stage (Binet B, C; Rai III, IV), diffuse bone-marrow infiltration or rapidly increasing blood lymphocyte levels, have a median survival probability of < 5 years and require therapy. Purine analogues are highly effective. Among these, fludarabine has become the treatment of choice for patients failing standard therapies. The role of purine analogues either alone or in combination with other drugs as front-line therapy is being investigated. Certain situations (e.g. autoimmune cytopenias, hypersplenism) require special treatment approaches (e.g. corticosteroids, splenectomy). Transplants of progenitor haematopoietic cells are also increasingly performed and deserve further investigation in younger patients with poor prognostic features. As a result of these advances, symptoms palliation is no longer the only possible goal in CLL therapy; sustained remissions and even cures are likely to be obtained in the near future.