Participants will receive IV infusion of obinutuzumab (100 milligrams [mg]) on Day 1 of Cycle 1; 900 mg administered on Day 2 of Cycle 1; and 1000 mg administered on Days 8 and 15 of Cycle 1 and on Day 1 of Cycles 2-6.

Participants will receive IV infusion of rituximab (375 mg/m^2) on Day 1 of Cycle 1 and 500 mg/m^2 administered on Day 1 of Cycles 2-6.

Participants will receive multiple doses of venetoclax orally once daily.

CR or CR with incomplete bone marrow recovery (CRi) or PR or nodular PR (nPR) was determined by the investigator according to IWCLL 2008 criteria. CR requires all of the following: Peripheral blood lymphocytes below 4x10^9/L, absence of lymphadenopathy by physical examination and computed tomography (CT) scan, No hepatomegaly or splenomegaly, Absence of disease or constitutional symptoms, Blood counts of neutrophils >1.5*10^9/L, platelets >100*10^9/L and hemoglobin >110 g/L, Bone marrow at least normocellular for age without clonal infiltrate (except for Cri). PR: two of the following features for at least 2 months: >/= 50% decrease in peripheral blood lymphocyte count from the pretreatment value, >/=50% reduction in lymphadenopathy, >/=50% reduction of liver and/or spleen enlargement, and at least one of the following blood counts: neutrophils >1.5*10^9/L, platelets >100*10^9/L and hemoglobin >110 g/L.

CR or CR with incomplete bone marrow recovery (CRi) or PR or nodular PR (nPR) was determined by the investigator according to IWCLL 2008 criteria. CR requires all of the following: Peripheral blood lymphocytes below 4x10^9/L, absence of lymphadenopathy by physical examination and computed tomography (CT) scan, No hepatomegaly or splenomegaly, Absence of disease or constitutional symptoms, Blood counts of neutrophils >1.5*10^9/L, platelets >100*10^9/L and hemoglobin >110 g/L, Bone marrow at least normocellular for age without clonal infiltrate (except for Cri). PR: two of the following features for at least 2 months: >/= 50% decrease in peripheral blood lymphocyte count from the pretreatment value, >/=50% reduction in lymphadenopathy, >/=50% reduction of liver and/or spleen enlargement, and at least one of the following blood counts: neutrophils >1.5*10^9/L, platelets >100*10^9/L and hemoglobin >110 g/L.

CR or CR with incomplete bone marrow recovery (CRi) was determined by the investigator according to IWCLL 2008 criteria. CR requires all of the following: Peripheral blood lymphocytes below 4x10^9/L, absence of lymphadenopathy by physical examination and computed tomography (CT) scan, No hepatomegaly or splenomegaly, Absence of disease or constitutional symptoms, Blood counts of neutrophils >1.5*10^9/L, platelets >100*10^9/L and hemoglobin >110 g/L, Bone marrow at least normocellular for age without clonal infiltrate (except for Cri).

PFS was determined according to IWCLL 2008 criteria and defined as the time from randomization to the first occurrence of progressive disease (PD) or death. Disease progression was characterized by at least one of the following: 1) >/= 50% increase in the absolute number of circulating lymphocytes to at least 5*10^9/L, 2) Appearance of new palpable lymph nodes (> 15 mm in longest diameter) or any new extra-nodal lesion; 3) >/= 50% increase in the longest diameter of any previous site of lymphadenopathy; 4) >/= 50% increase in the enlargement of the liver and/or spleen; 5) Transformation to a more aggressive histology.

OS was defined as the time from randomization to death from any cause.

An adverse event is any untoward medical occurrence in a subject administered a pharmaceutical product and which does not necessarily have to have a causal relationship with the treatment. An adverse event can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding, for example), symptom, or disease temporally associated with the use of a pharmaceutical product, whether or not considered related to the pharmaceutical product. Preexisting conditions which worsen during a study are also considered as adverse events.