The risk of immunosuppression deters many patients from receiving fludarabine, while combination chemotherapy regimens are poorly tolerated by elderly or infirm chronic lymphocytic leukemia (CLL) patients. Previous studies by our group and others have shown that rituximab is safe and well tolerated when used as a single agent in patients with CLL. In addition, maintenance therapy with rituximab was well tolerated by CLL patients, with probable prolongation of progression-free survival (Hainsworth et al. 2003). Based on pre clinical and clinical studies indicating possible increased efficacy of ofatumumab in patients with CLL, we wish to develop an antibody-only regimen for older patients and patients who refuse fludarabine-based regimens.