DISEASE CHARACTERISTICS:

          -  Histologically confirmed grade 1, 2, or 3 follicular non-Hodgkin lymphoma

               -  Stage II, III, or IV disease (according to the Ann Arbor staging system)

          -  CD20-positive disease

          -  Initial disease bulk ≤ 10 cm

          -  In first or second relapse after prior treatment with a rituximab-containing
             chemotherapy regimen (R-chemo) or chemotherapy alone

               -  Relapse must have occurred ≥ 6 months after completion of R-chemo

                    -  Relapse that occurred < 6 months after completion of chemotherapy alone
                       allowed

          -  Has at least one of the following symptoms requiring initiation of treatment:

               -  Nodal mass > 5 cm in its greater diameter

               -  B symptoms

               -  Elevated serum lactate dehydrogenase (LDH) or β2-microglobulin

               -  Involvement of ≥ 3 nodal sites (each with a diameter > 3 cm)

               -  Symptomatic splenic enlargement

               -  Compressive syndrome

          -  No primary refractory disease

          -  No large pleural or peritoneal effusions

          -  No CNS disease

        PATIENT CHARACTERISTICS:

          -  ECOG performance status 0-2

          -  Life expectancy ≥ 6 months

          -  Absolute granulocyte count ≥ 1,500/mm³

          -  Platelet count ≥ 1,000/mm³

          -  Serum creatinine < 1.5 times upper limit of normal (ULN)

          -  Total bilirubin < 1.5 times ULN

          -  AST < 5 times ULN

          -  No active obstructive hydronephrosis

          -  No evidence of active infection requiring IV antibiotics

          -  No advanced heart disease or other serious illness that would preclude study
             evaluation

          -  No known HIV infection

          -  No human anti-mouse antibody (HAMA) reactivity

          -  No known hypersensitivity to murine antibodies or proteins

          -  Not pregnant or nursing

          -  Negative pregnancy test

          -  Fertile patients must use effective contraception during and for 12 months after
             completion of study treatment

          -  No other prior malignancy, except for adequately treated skin cancer, cervical cancer
             in situ, or other cancer for which the patient has been disease-free for 5 years

        PRIOR CONCURRENT THERAPY:

          -  See Disease Characteristics

          -  At least 4 weeks since prior investigational drugs and recovered

          -  No prior radioimmunotherapy