Much progress has been made in delineating the pathogenesis of multiple myeloma and chronic lymphocytic leukemia. The cell of origin in both diseases has been better defined, which has led to important clinical treatments. For myeloma, reduction of tumor burden in autografts has been accomplished and been associated with favorable outcome. The importance of interleukin-6 in maintaining this tumor and causing skeletal disease has been more clearly defined and has led to treatment with antibodies that block this cytokine's action. The bisphosphonate pamidronate decreases skeletal complications and improves quality of life for these patients. For chronic lymphocytic leukemia, further definition of common cytogenetic and gene abnormalities have been made and associated with patient outcome. The nucleoside analogues continue to produce excellent responses and the use of myeloablative chemotherapy with hematopoietic support shows promise in early studies.