Inclusion Criteria:

- Patients must have a histologically confirmed CD20 +ve follicular lymphoma grades I
to IIIa.

- Patients with at least one of the following symptoms requiring initiation of
treatment: (as outlined by the modified BNLI/GELF criteria below)

- Nodal mass > 7cm in its greater diameter

- B symptoms

- Elevated serum LDH or beta2-microglobulin

- involvement of at least 3 nodal sites (each with a diameter > 3 cm)

- symptomatic splenic enlargement

- compressive syndrome

- Patients must have an ECOG performance status less than or equal to 2 and an
anticipated survival of at least 6 months.

- Patients must have an absolute granulocyte count of above 1,500/mm3, and a platelet
count of above 100,000/mm3 post 4 weeks of unlabelled Rituximab. A hemoglobin >= 8.0
g/dl

- Patients must have adequate renal function (defined as calculated creatinine
clearance > 30 ml/mn), hepatic function (defined as total bilirubin <1.5 times upper
limit of normal), and hepatic transaminases (defined as AST <5 times upper limit of
normal)

- Patients must have given informed consent prior to study entry.

Exclusion Criteria:

- Patients with a mean of >20% of the intratrabecular marrow space involved with
lymphoma on bone marrow biopsy following induction Rituximab therapy.

- Transformed follicular lymphoma and discordant lymphoma

- Patients with active obstructive hydronephrosis.

- Patients with initial disease bulk greater than 10cm.

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

- Patients with congestive heart failure stage III or IV of NYHA classification,
myocardial infraction or unstable angina within 6 months or other serious illness
that would preclude evaluation.

- Patients with left VEF < 40%

- Patients with large pleural or peritoneal effusions.

- Patients with known HIV infection or active HBV (HbsAg positivity) or HCV infection.

- Known Hypersensitivity to murine antibodies or proteins

- Patients who are pregnant or breast-feeding. Male and female patients must agree to
use effective contraception for 12 months following 90Y-ibritumomab tiuxetan antibody
therapy.

- Patients with prior malignancy other than lymphoma, except for adequately-treated
skin cancer, cervical cancer in situ, or other cancer for which the patient has been
disease-free for 5 years.