Inclusion Criteria:

- Patient > 50 years old

- Follicular lymphoma grade I, II, or IIIa according to REAL/WHO classification

- Ann Arbor stage III, or IV, or stage II with disseminated abdominal disease requiring
extensive abdominal irradiation

- No prior chemotherapy, immunotherapy, or irradiation. Furthermore, when receiving
therapy as part of this "Zevalin® first line in follicular lymphoma" trial and up to
six months after therapy has ended, patients may not participate in another clinical
trial. If patients receive consolidation therapy with Rituximab, the six months
period is counted from the end of the consolidation therapy.

- Lymphoma cells positive for CD20

- Measurable disease (two perpendicular diameters by either physical or radiological
examination)

- WHO/ECOG performance status 0 - 2

- Written informed consent

Exclusion Criteria:

- Bone marrow involvement only

- Bone marrow infiltration > 25%

- Leukocytopenia < 2.500 /µl

- Thrombocytopenia < 100.000 /µl

- Bulk lesions > 10 cm

- CNS lymphoma manifestation

- Circulating tumor cells > 500 /µl

- Extensive pleural effusion/ascites (> 1000 ml as estimated by ultrasound/CT)

- Severe concomitant diseases (e.g. congestive heart failure, myocardial infarction
within 6 months of study, severe uncontrolled hypertension, renal insufficiency
requiring hemodialysis, pulmonary disease, liver disease)

- Abnormal liver function: transaminases or total bilirubin > 2 x upper limit of normal
(ULN) (unless caused by the lymphoma)

- Abnormal renal function: serum creatinine > 2 x upper limit of normal (unless caused
by the lymphoma)

- Previous malignancy other than non-melanoma skin cancer

- Pregnant or breast feeding female patients (negative pregnancy test required for
women of fertile age), no effective contraception

- HIV positivity

- Known hypersensitivity to foreign proteins, murine antibodies, presence of human
anti-murine antibodies (HAMA) reactivity

- Severe psychiatric illness