Study Combining Zevalin With High-Dose Chemotherapy Prior to Autologous StemCell Transplant in Patients With Relapsed, Refractory, or Transformed Non-Hodgkin's Lymphoma

Inclusion Criteria: 1. Age \>=18 to \<=70 years 2. Relapsed or refractory Stage III or IV, grade 1,2, or 3 Follicular Lymphoma or transformed follicular lymphoma, mantle cell lymphoma, marginal zone lymphoma, Waldenstrom's macroglobulinemia, or diffuse large B-Cell lymphoma as defined by the WHO and: * Expressing the CD 20 antigen * ECOG performance 0-2 * Written informed consent 3. Prior collection of at least 2.5x10\^6 CD34-positive peripheral blood stem cells/kg. Exclusion Criteria: 1. Abnormal renal function (Creatinine \>2.5x upper limit of normal (ULN) 2. Abnormal hepatic function (Bilirubin \>2xULN, ALT/AST \>3x ULN) 3. Cardiac ejection fraction \<40% 4. Severe defects in pulmonary function tests (DLCO\<70% predicted, FEV1, FVC\<60% predicted) or receiving continuous oxygen 5. A history of human anti-mouse antibodies (HAMA) or known type 1 hypersensitivity or anaphylactic proteins to any component of the Zevalin therapy. 6. Female patients who are pregnant or breast feeding, and adults of reproductive potential who are not employing an effective method of birth control during study treatment 7. Prior radiotherapy to \>25% of the bone marrow or \>20 Gy to critical organ (lung, liver, kidney, spinal cord). 8. CNS lymphoma 9. Ongoing infection 10. Prior treatment with radioimmunotherapy