Chronic lymphocytic leukemia (CLL) is the commonest leukemia in adults and, until recently, had limited treatment options. However, the combination of fludarabine, cyclophosphamide, and rituximab (FCR) produces impressive clinical responses and prolongs survival of many CLL patients with symptomatic disease. Unfortunately, FCR is a toxic regimen that cannot generally be tolerated by patients over the age of 65 years who constitute more than 70% of the CLL patient population. In addition, FCR is contraindicated in patients whose leukemia cells harbor deletions of chromosome 17, where the tumor suppressor p53 is located, because such cells are intrinsically resistant to genotoxic drugs. This group constitutes 10-15% of patients of all ages who require first-line therapy. Better therapies for these two large groups of patients are needed.