This open-label, 2-arm, nonrandomized, multicenter, Phase Ib study will investigate the safety and efficacy of obinutuzumab (RO5072759; GA101) administered in combination with chemotherapy (bendamustine or fludarabine + cyclophosphamide \[FC\] regimens) in participants with previously untreated cluster of differentiation 20 (CD20)-positive B-CLL. Participants will be enrolled to receive a maximum of 6 cycles of obinutuzumab (1000 milligrams \[mg\] intravenous \[IV\] infusion, on Days 1, 8 and 15 of Cycle 1 and Day 1 of Cycles 2 - 6) plus bendamustine (90 milligrams per meter square \[mg/m\^2\] IV, on Days 2 and 3 of Cycle 1 and Days 1 and 2 of Cycles 2 - 6) on 28 day cycles or a maximum of 6 cycles of obinutuzumab (1000 mg IV infusion, on Days 1, 8 and 15 of Cycle 1 and Day 1 of Cycles 2 - 6) plus FC (fludarabine 25 mg/m\^2 IV on Days 2, 3 and 4 of Cycle 1 and Days 1, 2 and 3 of Cycles 2 - 6; cyclophosphamide 250 mg/m\^2 IV on Days 2, 3 and 4 of Cycle 1 and Days 1, 2 and 3 of Cycles 2 - 6) on 28 day cycles.