Inclusion Criteria:- Histologically confirmed low grade CD20+ B cell NHL patients who have relapsed after chemotherapy or are chemotherapy resistant and have one or more sites of disease measuring more than 5 cm.

• The patients must have failed at least one chemotherapy regimen
• No anticancer treatment for three weeks prior to study initiation (six weeks if Rituximab, nitrosourea or Mitomycin C), and fully recovered from all toxicities associated with prior surgery, radiation, chemotherapy or immunotherapy
• An IRB approved signed informed consent
• Age greater and or equal to 19 years
• Expected survival of at least 6 months
• Prestudy Performance Status of 0, 1 or 2 according to the WHO

• Acceptable laboratory status within 2 weeks prior to patient enrollment including:

  • ANC of at least 1,500/mm^3, platelet count at least 100,000/mm3, Hct greater than 30% and Hgb greater than 9.0 gm
  • Bilirubin less than or equal to 2.0, Creatinine less than or equal to 2.0
  • Bone marrow involvement with lymphoma less than 25% (bilateral bone marrow) within 6 weeks of enrollment
• Acceptable birth control method for men and women of reproductive potential
• Female patients who are not pregnant or lactating Exclusion Criteria:- Disease progression within 3 months of last chemotherapy
• Prior myeloablative therapies with bone marrow transplantation or peripheral stem cell rescue

• Patients with impaired bone marrow reserve as indicated by one or more of the following:

  • Platelet count less than 100,000/mm^3
  • Hypocellular bone marrow (less than or equal to 15% cellularity)
  • Marked reduction in bone marrow precursors of one or more cell lines
  • History of failed stem cell collection
• Prior treatment with Fludarabine
• Prior radioimmunotherapy
• Presence of CNS lymphoma
• Patients with HIV or AIDS-related lymphoma
• Patients with evidence of myelodysplasia on bone marrow biopsy or abnormal bone marrow cytogenetics
• Patients who have received prior external beam radiation therapy to more than 25% of active bone marrow
• Patients who have received G-CSF or GM-CSF therapy within 3 weeks prior to treatment
• Pregnant or lactating women
• Presence of HAMA reactivity in patients with prior exposure to murine antibodies or proteins
• Serious nonmalignant disease or infection, which, in the opinion of the investigator and/or sponsor, would compromise other protocol objectives
• Another primary malignancy (other than squamous cell and basal cell CA of the skin, in situ CA of the cervix, or treated prostate cancer with stable PSA) for which the patients has not been disease free for at least 3 years
• Major surgery, other than diagnostic surgery, within 4 weeks
• Patients with pleural effusion