Inclusion Criteria:

- Male or female subjects age 18 to 80 years, inclusive, with any International
Prognostic Index score; treated with 6 or more cycles of first-line CHOP chemotherapy
and achieved a PR, CRu, or CR

- de novo diffuse large B cell NHL according to the REAL classification; Ann Arbor
stage III, stage IV, or bulky stage II disease (any mass ≥10 cm in diameter)

- less than an average of 25% of the intratrabecular marrow space involved by NHL in
bilateral bone marrow biopsy specimens or <10% involvement with NHL from unilateral
bone marrow biopsy; tumor tissue expressing the CD20 antigen

- ≥60% performance status on the Karnofsky Performance Scale and an anticipated
survival of at least 3 months

- absolute neutrophil count (ANC) ≥1500 cells/mm3 and platelet count ≥100,000/mm3

- adequate renal function (serum creatinine <1.5 × upper limit of normal [ULN]) and
hepatic function (total bilirubin ≤2.0 × ULN and aspartate aminotransferase <5 × ULN)

Exclusion Criteria:

- Prior radiation, prior biological therapy, or prior chemotherapy other than
first-line CHOP

- active bilateral obstructive hydronephrosis

- New York Heart Association class III or IV heart disease or other serious illness

- prior malignancy other than lymphoma (except for adequately treated skin cancer, in
situ cervical cancer, or other cancer for which they had been disease-free for >5
years)

- human immunodeficiency virus infection

- HAMA positive

- brain or leptomeningeal metastases at any time since diagnosis

- active infection requiring intravenous anti-infectives

- pregnant or breastfeeding