Inclusion Criteria:

- Histologically confirmed low-grade or transformed NHL with evaluable, measurable
disease

- Tumor had to express CD20 antigen

- One to three prior chemotherapy regimens

- Karnofsky performance score ≥60% and anticipated survival ≥3 months

- Absolute neutrophil count (ANC) >1500/mm3 and platelet count >100,000/mm3

- Adequate renal and hepatic function

- 18 years of age or older.

- Written informed consent and sign an IRB-approved Informed consent from prior to
study entry.

Exclusion Criteria:

- More than an average of 25% of the intratrabecular marrow space involved by lymphoma
in bone marrow biopsy specimens as assessed microscopically within 42 days of study
entry. Bilateral posterior iliac crest core biopsies are required if the percentage
of intratrabecular space involved exceeds 10% on a unilateral biopsy. The mean of
bilateral biopsies must be no more than 25%.

- Received cytotoxic chemotherapy, radiation therapy, immunosuppressants, or cytokine
treatment within FOUR weeks prior to study entry (6 weeks of nitrosourea compounds)
or who exhibit persistent clinical evidence of toxicity. The use of steroids must be
discontinued at least 1 week prior to study entry.

- Have undergone prior stem cell transplant.

- Active obstructive hydronephrosis.

- Evidence of active infection requiring intravenous antibiotics at the time of study
entry.

- New York Heart Association class III or IV heart disease or other serious illness
that would preclude evaluation.

- Prior malignancy other than lymphoma, except for adequately-treated skin cancer, in
situ cervical cancer, or other cancer for which subject has been disease-free for 5
years.

- Known HIV infection.

- Known brain or leptomeningeal metastases.

- Pregnant or nursing. Subjects of childbearing potential must undergo pregnancy test
within 7 days of study entry and antibody is not to be administered until a negative
result is obtained. For those subjects in Arm B, the pregnancy test must be repeated
within 7 days of crossover. Male and female must agree to use effective contraception
for 6 months following the therapeutic dose, as applicable.

- Previous allergic reactions to iodine. This does not include reactions to intravenous
iodine-containing contrast materials.

- Previously given any monoclonal or polyclonal antibodies of any non-human species for
either diagnostic or therapeutic purpose. This includes engineered chimeric and
humanized antibodies.

- Previously received radioimmunotherapy .

- Progressive disease within one year of irradiation arising in a field that has been
previously irradiated with >3500 cGy.

- de novo intermediate or high-grade lymphoma.

- Received >3 chemotherapy regimens (different or identical agents).