Summary of major inclusion and exclusion criteria. Other Safety criteria will need to be
met.

Inclusion Criteria:

- Histologically confirmed, relapsed or refractory CD20+ follicular B-cell NHL within
12 months of Study Day 1 (without clinical evidence of transformation). NHL must
require treatment as determined by an increase in overall tumor size. The presence
of B symptoms, and/or the presence of masses which are causing ongoing clinical
symptoms.

- Bidimensionally measurable disease meeting the minimum requirement of at least 1
lesion >/= 2.0 cm in a single dimension.

- No lymphoma therapy for 3 weeks prior to Study Day 1.

- Patients must be recovered from all toxicities associated with prior surgery,
radiation therapy, chemotherapy, or immunotherapy.

- Signed IRB-approved informed consent.

- Greater than 18 years of age.

- Expected survival >/= 3 months.

- WHO performance status of
- Acceptable hematologic status, liver function, renal function, and pulmonary
function.

- Female patients who are not pregnant or lactating.

- Men and women of reproductive potential who are following accepted birth control
methods.

Exclusion Criteria:

- Patients with impaired bone marrow reserve, which may be indicated by prior
myeloablative therapy with autologous bone marrow transplantation (ABMT) or
peripheral blood stem cell (PBSC) rescue.

- Prior radioimmunotherapy, including the Zevalin regimen.

- Prior immunotherapy, including Rituxan therapy within 6 months of Study Day 1.

- Rituxan-refractory (no response to most recent Rituxan-containing regimen, or TTP was
< 6 months).

- Presence of CNS lymphoma.

- Patients with chronic lymphocytic leukemia (CLL).

- Known history of HIV or AIDS.

- Serious nonmalignant disease or infection

- Major surgery, other than diagnostic surgery, within 4 weeks of Study Day 1.

- Patients who received investigational product within 4 weeks of Study Day 1 or
patients who may experience long-term toxicity from a previous investigational
therapy.