Inclusion Criteria:

- Adult patients, >/= 18 and
- Histologically confirmed, previously untreated CD20+ diffuse large B-cell lymphoma
(DLBCL) or CD20+ follicular non-Hodgkin's lymphoma (NHL) Grade 1, 2, or 3a, according
to WHO classification

- An International Prognostic Index (IPI) score of 1-4 or IPI score of 0 with bulky
disease, defined as one lesion >/= 7.5 cm, or Follicular Lymphoma International
Prognostic Index (FLIPI; low, intermediate or high risk)

- At least one bi-dimensionally measurable lesion defined as >/=1.5 cm in its largest
dimension on CT scan

- Eastern Cooperative Oncology Group (ECOG) performance status
Exclusion Criteria:

- Transformed lymphoma or follicular lymphoma IIIB

- Primary central nervous system (CNS) lymphoma, blastic variant of mantle-cell
lymphoma, histologic evidence of transformation to Burkitt lymphoma, primary
mediastinal DLBCL, primary effusion lymphoma, primary cutaneous DLBCL, or primary
DLBCL of the testis

- History of other malignancy that could affect compliance with the protocol or
interpretation of the results; this includes a malignancy that has been treated but
not with curative intent, unless the malignancy has been in remission for >/= 5 years
prior to enrolment; patients with a history of curatively treated basal or squamous
cell carcinoma or melanoma of the skin or in situ carcinoma of the cervix are
eligible

- Prior therapy for DLBCL or NHL, with the exception of nodal biopsy or local
irradiation

- Prior treatment with cytotoxic drugs (with the exclusion of methotrexate for CNS
prophylaxis in DLBCL) or rituximab for another condition, or prior use of an
anti-CD20 drug

- Prior use of monoclonal antibody within 3 months prior to randomization

- Chemotherapy or other investigational therapy within 28 days prior to randomization

- Ongoing corticosteroid use > 30 mg/day prednisolone or equivalent

- Inadequate renal. hematologic or hepatic function

- Active and/or severe infection or any major episode of infection within 4 weeks prior
to randomization

- Active hepatitis B virus or active hepatitis C virus infection

- History of human immunodeficiency (HIV) seropositive status

- A positive pregnancy test in women of childbearing potential

- Life expectancy of less than 6 months