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. TOC:B Cell Development and Its Deregulation to Transformed States at the Pre B Cell Receptor - Expressing Pre BII Cell Stage.- Gene Expression Patterns in Human and Mouse B Cell Development.- New Insights Into the Phenotype and Cell Derivation of B-Cell Chronic Lymphocytic Leukemia.- Chronic Lymphocytic Leukemia: Molecular Genetics and Animal Models.- What Do Somatic Hypermutation and Classic Switch Recombination Teach Us About Chronic Lymphocytic Leukemia Pathogenesis.- Chronic Lymphocytic Leukemia: A Review of the Immunoarchitecture.- Clinical and Laboratory Parameters That Define B-CLL Subgroups of Clinical Relevance.- Differential Effects on CLL Cell Survival Exerted by Different Microenvironmental Elements.- Genotypic Prognostic Markers.- Chronic Lymphocytic Leukemia: Clinical Translations of Biological Features.- Subject Index.