Forty patients will receive therapy on this study at the 2 clinical sites. Patients will undergo 2 phases of the study. In the first phase, termed the "dosimetric dose", patients will receive an infusion of unlabeled Anti B1 Antibody (450 mg) over 70 minutes (including a 10 minute flush) immediately followed by a 30 minute infusion (including a 10 minute flush) of Anti B1 Antibody (35 mg) which has been trace-labeled with 5 mCi of Iodine 131. Whole body gamma camera scans will be obtained on 1) Day 0; 2) Day 2, 3, or 4; and 3) Day 6 or 7 following the dosimetric dose. Using the dosimetric data from the 3 imaging timepoints, a patient-specific dose of Iodine 131 Anti B1 Antibody to deliver the desired total body dose of radiotherapy will be calculated. In the second phase, termed the "radioimmunotherapeutic dose", patients will receive a 70 minute infusion (including a 10 minute flush) of unlabeled Anti B1 Antibody (450 mg) immediately followed by a 30 minute infusion (including a 10 minute flush) of 35 mg Anti B1 Antibody labeled with the patient-specific dose of Iodine 131 to deliver a whole body dose of 75 cGy to patients with no hematologic risk factors. Patients who have platelet counts of 100,001-149,999 cells/mm3 will receive 65 cGy and patients who are obese will be dosed based upon 137% of their lean body mass (see Appendix A). Patients will be treated with either saturated solution potassium iodide (SSKI), Lugol's solution, or potassium iodide tablets starting at least 24 hours prior to the first infusion of the Iodine 131 Anti B1 Antibody and continuing for 14 days following the last infusion of Iodine 131 Anti B1 Antibody (i.e., therapeutic dose).