B-cell chronic lymphocytic leukemia (B-CLL), the leukemia with highest incidence in Western Countries, is a neoplastic disease characterized by a progressive accumulation of functionally incompetent, long-lived small mature lymphocytes in the blood, bone marrow, and lymphoid tissues. B-CLL lymphocytes express characteristic low amounts of surface immunoglobulin and CD5 antigen. They are resistant to Epstein Barr Virus (EBV) transformation; are in prolonged G0 phase, express high amounts of bcl-2 and display a defective response to stimulation through the antigen receptor. Despite the presence of many genetic abnormalities, in CLL, there are no typical chromosomal aberrations or oncogenic abnormalities associated with this disease.