Any cell of the immune system can undergo malignant transformation giving rise to leukemia, lymphoma, or myeloma. We focus on B-cell-type chronic lymphocytic leukemia (B-CLL), the most common leukemia in the Western Hemisphere. This B-cell lymphoproliferative disorder arises among the aging population, increasing in incidence in a linear fashion after age 50. Therefore, its incidence is likely to increase as the baby boomer generation enters the sixth decade. Because patients with the disease in general have an extended clinical course (three to twenty-five years), B-CLL is categorized as one of a group of indolent leukemias/lymphomas. However, despite progress in therapeutic strategies, B-CLL remains an incurable disease.