Recent studies have improved our understanding of the cytogenesis, biology, and therapy of chronic lymphocytic leukemia (CLL). This review highlights this recent progress reported over the past year. We have improved our understanding of the cytogenetic abnormalities in CLL and soon may see identification of new tumor suppressor genes that may be deleted in the leukemia cells of a large number of patients with this disease. We have achieved a better understanding of the surface antigens that help govern the pattern of tissue-infiltration of leukemia cells in vivo. Studies on the immune pathophysiology of CLL are providing clues to potential mechanisms leading to the immunodeficiency associated with this disease. Combination chemotherapy with purine analogues is showing promise for improved efficacy in CLL. Finally, new therapies incorporating bone marrow transplantation, and possibly gene therapy, increasingly are being considered for the therapy of patients with this disease.