A comprehensive and critical review of the latest scientific advances in our understanding of the molecular genetics and biology of CLL and their application to the best management of CLL. The authors focus on diagnosis, prognosis, multifaceted treatment options, and complications. Among the diverse treatments considered are chemotherapy, autologous and allogenic transplantations, monoclonal antibody therapy, immunotoxin therapy, gene therapy, and several new therapeutic strategies. Familial and juvenile chronic lymphocytic leukemia are also discussed.