In this trial, we will evaluate the feasibility, toxicity, and effectiveness ibritumomab tiuxetan, when incorporated into combination first-line treatment for follicular lymphoma. Addition of the ibritumomab tiuxetan to our previously evaluated, well tolerated combination of rituximab and short course chemotherapy will allow the use of additional active agent with a unique mechanism of cytotoxicity. In addition, "debulking" of lymphoma prior to 90Y Zevalin administration may minimize the myelotoxicity of this agent.

Upon determination of eligibility, patients will be receive:

• Rituxan + CHOP or CVP + Ibritumomab Tiuxetan

Patients who are considered medical candidates for doxorubicin should receive CHOP chemotherapy (Cyclophosphamide, doxorubicin, vincristine and prednisone). Patients who are not considered medical candidates for doxorubicin should receive CVP chemotherapy (Cyclophosphamide, Vincristine, and prednisone)

Inclusion Criteria:

To be included in this study, you must meet the following criteria:

• Histologic documentation of follicular center, B-cell lymphoma
• Early stage lymphoma (stages I or II) relapsed after radiation therapy alone
• No previous chemotherapy or monoclonal antibody therapy
• Measurable or evaluable disease
• Able to perform activities of daily living with minimal assistance
• Age > 18 years
• Adequate bone marrow ,liver and kidney function
• Must be accessible for treatment and follow-up.
• Bone marrow examination initial staging and accurate restaging
• All patients must give written informed consent prior to study entry.

Exclusion Criteria:

You cannot participate in this study if any of the following apply to you:

• Small lymphocytic (CLL type) lymphomas and CLL
• Impaired bone marrow reserve
• Female pregnant or lactating
• Serious active infection at the time of treatment
• Any other serious underlying condition
• Central nervous system involvement (brain or meningeal)
• HIV or AIDS-related lymphoma
• Received prior external beam radiation therapy to > 25% of active bone marrow
• Pleural effusion
• Received prior murine antibodies or proteins
• History of other neoplasms within five years of diagnosis

Please note: There are additional inclusion/exclusion criteria. The study center will determine if you meet all of the criteria. If you do not qualify for the trial, study personnel will explain the reasons. If you do qualify, study personnel will explain the trial in detail and answer any questions you may have.