Chronic lymphocytic leukaemia (CLL) is the most common leukaemia in the Western world. It is also the prototype of B-cell chronic lymphoid malignancies and of their ramifications within the fields of hematology, immunology and oncology. For a long time the Cinderella of lymphoid malignancies CLL has now become the focus of major interest and an increasing number of investigators from different areas, including genetics, molecular biology, basic and applied immunology are becoming actively engaged in the investigation of CLL. Clinicians are considering CLL as a very interesting target of many projects which aim at translating the new and exciting developments of basic science into effective new approaches to the patient.