 OUTLINE: Patients receive rituximab intravenously IV followed by, no more than 4 hours later, indium In 111 ibritumomab tiuxetan for imaging IV over 10 minutes on day -21. Patients undergo gamma camera imaging on day -19. Patients receive rituximab IV followed by, no more than 4 hours later, yttrium Y 90 ibritumomab tiuxetan IV over 10 minutes on day -14. Patients also receive fludarabine phosphate IV over 30-60 minutes on days -7 to -5 and undergo low-dose total-body irradiation TBI on day 0. After TBI, patients undergo allogeneic peripheral blood stem cell transplantation PBSCT on day 0. Patients who undergo PBSCT from a related donor receive oral cyclosporine twice daily on days -3 to 56 followed by a taper to day 180 in the absence of graft-versus-host disease GVHD. These patients also receive oral mycophenolate mofetil twice daily on days 0 to 27. Patients who undergo PBSCT from an unrelated donor receive oral cyclosporine twice daily on days -3 to 100 followed by a taper over 11 weeks in the absence of GVHD. These patients also receive oral mycophenolate mofetil three times daily on days 0 to 40 followed by a taper to day 96. 