An Open-label, Multi-center, Three Arm Randomized Study to Investigate the Safety and Efficacy on Progression-free Survival of RO5072759 + Chlorambucil (GClb) Compared to Rituximab + Chlorambucil (RClb) or Chlorambucil (Clb) Alone in Previously Untreated CLL Patients With Comorbidities.

Inclusion Criteria:

- Adults >/=18 years

- Documented CD20+B-CLL

- Previously untreated CLL requiring treatment according to the NCI criteria

- Total CIRS > 6 and/or creatinine clearance < 70 ml/min

Exclusion Criteria:

- Prior CLL therapy

- Transformation of CLL to aggressive NHL (Richter's transformation)

- History of other malignancy unless the malignancy has been in remission without
treatment for >/=2 years prior to enrolment, and except for carcinoma in situ of the
cervix, basal or squamous cell skin cancer, surgically treated low-grade prostate
cancer, or DCIS of the breast treated with lymphectomy alone

- Positive hepatitis serology (HBV, HCV) or positive HIV or HTLV testing

- Patients with active infection requiring systemic treatment