Inclusion Criteria:

- Patients must have a histologically-confirmed diagnosis of B-cell CLL/PLL/SLL;
lymphoplasmacytic - immunocytoma; follicle center, follicular, grade I; or follicle
center, follicular, grade II NHLs or one of these B-cell lymphomas which has
transformed to a more aggressive histology (37).

- Patients must have evidence that their tumor tissue expresses the CD20 antigen.
Immunoperoxidase stains of paraffin-embedded tissue showing positive reactivity with
L26 antibody or immunoperoxidase stains of frozen tissue showing positive reactivity
with Anti B1 Antibody (>50% of tumor cells are positive) or evidence of CD20
positivity by flow cytometry (>50% of tumor cells are positive) are acceptable
evidence of CD20 positivity. Testing of tumor tissue from any time in the course of
the patient's disease is acceptable.

- Patients must have received 1 or 2 prior chemotherapy regimens and have progressed
following their last regimen. Patients who have received >2 prior chemotherapy
regimens are excluded. Prior therapy with radiation, immunosuppressants, or steroids
are not counted as chemotherapy regimens.

- Patients must have a performance status of at least 60% on the Karnofsky Scale (see
Appendix B) and an anticipated survival of at least 3 months.

- Patients must have an absolute granulocyte count >1,500 x 109/l and a platelet count
>100,000 x 109/l within 14 days of study entry. These blood counts must be sustained
without support of hematopoietic cytokines or transfusion of blood products.

- Patients must have adequate renal function (defined as serum creatinine <1.5 upper
limit of normal) and hepatic function (defined as total bilirubin <1.5 upper limit of
normal and hepatic transaminases [AST + ALT] <5 x upper limit of normal) within 14
days of study entry.

- Patients must have bi-dimensionally measurable disease. At least one lesion must be
>/=2cm x 2 cm (by CT scan).

- Patients must be at least 18 years of age.

- Patients must give written informed consent and sign an EC-approved informed consent
form prior to study entry.

Exclusion Criteria:

- Patients with 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%. The
procedure for bilateral bone marrow biopsy analysis of marrow involvement is included
in Appendix C.

- Patients who have received cytotoxic chemotherapy, radiation therapy, or cytokine
treatment within 4 weeks prior to study entry (6 weeks for nitrosourea compounds) or
who exhibit persistent clinical evidence of toxicity. The use of systemic steroids
must be discontinued one week prior to study entry.

- Patients with prior hematopoietic stem cell transplant following high-dose
chemotherapy or chemo/radiotherapy.

- Patients with active obstructive hydronephrosis.

- Patients with evidence of active infection requiring IV antibiotics at the time of
study entry.

- Patients with New York Heart Association class III or IV heart disease (see Appendix
D) or other serious illness that would preclude evaluation.

- Patients with prior malignancy other than lymphoma, except for adequately-treated
skin cancer, in situ cervical cancer, or other cancer for which the patient has been
disease-free for 5 years. Patients who have been disease-free of another cancer for
greater than 5 years must be carefully assessed at the time of study entry to rule
out recurrent disease.

- Patients with known HIV infection.

- Patients with known brain or leptomeningeal metastases.

- Patients who are pregnant or breast-feeding. Patients of child-bearing potential
must undergo a serum pregnancy test within 7 days prior to study entry and
radiolabeled antibody is not to be administered until a negative result is obtained.
Males and females must agree to use effective contraception for 6 months following
treatment.

- Patients with previous allergic reactions to iodine. This does not include reacting
to IV iodine-containing contrast materials.

- Patients who were previously given any monoclonal or polyclonal antibodies of any
non-human species for either diagnostic or therapeutic purposes. This includes
engineered chimeric and humanized antibodies.

- Patients who previously received radioimmunotherapy.

- Patients with progressive disease within 1 year of irradiation arising in a field
that has been previously irradiated with >3500 cGy.

- Patients who are concurrently receiving either approved or non-approved (through
another protocol) anti-cancer drugs or biologics.

- Patients who have received more than 2 prior chemotherapy regimens. Prior therapy
with radiation, immunosuppressants, or steroids are not counted as chemotherapy
regimens.