This single arm study will assess the efficacy and safety of MabThera + chlorambucil as induction therapy, followed in responders by maintenance therapy or observation in elderly patients with previously untreated chronic lymphocytic leukemia. During the induction phase patients will receive 2 x 4 weekly courses of chlorambucil followed by 8 x 4 weekly courses of chlorambucil + MabThera. Subsequently, responders will be randomized to receive 12 doses of MabThera given every 8 weeks, or no further treatment. The anticipated time on study treatment is 2+ years, and the target sample size is <100 individuals.