 Patients receive a dosimetric dose of iodine I 131 tositumomab intravenously IV over 40-60 minutes on day -24 followed by gamma camera imaging over the next 6 days. Patients then receive a therapeutic dose of iodine I 131 tositumomab via central line over 40-60 minutes on day -14. Patients also receive fludarabine phosphate IV once daily QD on days -11 to -9 OR days -11 or -7. Patients undergo autologous or syngeneic peripheral blood stem cell transplantation on day 0. 