Inclusion Criteria:

- Adult patients, >/= 18 years of age

- Previously untreated CD20-positive diffuse large B-cell lymphoma

- Ann Arbour Stage III/IV and bulky II (mass >10 cm)

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

- Eastern Cooperative Oncology Group (ECOG) performance status 0, 1 or 2

- Left ventricular ejection fraction >/= 50%

- Adequate hematologic function

Exclusion Criteria:

- Transformed lymphoma (follicular IIIB) if previously treated with chemotherapy or
immunotherapy

- Prior therapy for diffuse large B-cell lymphoma except for nodal biopsy or local
irradiation

- CNS lymphoma, primary mediastinal large cell lymphoma, primary cutaneous lymphoma,
primary effusion lymphoma

- Patients who received cytotoxic drugs or rituximab as part of their treatment for
another condition (e.g. rheumatoid arthritis) or prior use of an anti-CD20 antibody

- Chemotherapy or other investigational therapy within 28 days prior to the start of
Cycle 1

- Contraindication to any of the individual components of CHOP, including prior receipt
of anthracyclines

- History of severe allergic or anaphylactic reactions to monoclonal antibody therapy

- History of other malignancy, except for curatively treated basal or squamous cell
carcinoma or melanoma of the skin or in situ carcinoma of the cervix, or malignancy
treated with or without curative intent and in remission without treatment for >/=2
years prior to enrolment

- Positive for hepatitis B, hepatitis C, HIV or HTLV-1 infection

- Pregnant or lactating women