This is a randomized, open label, phase III study to evaluate the ability of rituximab maintenance therapy to prolong event-free survival in aggressive NHL.

Patients will be screened after successful standard induction therapy (CR or Cru following standard R-CHOP-like therapy with 8 infusions of rituximab plus CHOP-like chemotherapy (4-8 cycles). Patients will be followed until an event occurs as defined in the protocol. To evaluate the clinical efficacy of rituximab maintenance therapy as compared to observation in patients with aggressive B-cell Non-Hodgkins lymphoma or follicular lymphoma grade 3b who have achieved a complete remission after appropriate first-line therapy, measured by event-free survival (EFS), 440 patients with DLCBL or follicular NHL grade 3 (220 per arm) will be recruited.

Inclusion Criteria:

• 4 to 8 cycles R-CHOP/like, total of 8x Rituximab
• CR, CRu
• ECOG/ 0.1 or 2
• Known IPI at time of diagnosis
• Age > 18 years
• Negative pregnancy test
• Men must agree not to father a child during the therapy

Exclusion Criteria:

• Transformed lymphoma
• Secondary malignancy
• Evidence of CNS - involvement
• Significant cardiac disease
• Creatinine > 2.0 mg/dl
• HIV, Hepatitis positive