Phase II Study of Campath-1H Antibody to Treat Waldenstrom's Macroglobulinemia

* Patients will receive 3 test doses of Campath-1H (3mg, 10mg, 30mg). If the patient tolerates these three test doses, then they will receive a total of 6 weeks of Campath-1H therapy three times a week. * After the patient receives the first 6 weeks of therapy at the 30mg therapeutic dose they will be re-assessed by blood testing. If it is determined that their disease has progressed in the period of time while the patient was on Campath-1H, the patient will be removed from the study. * If it is determined that the patient has achieved a complete remission after 6 weeks of Campath-1H treatment a bone marrow biopsy will be performed to confirm complete remission and the patient will not receive any additional treatment but will be followed for a period of 2 years. * If the disease has remained stable or partial response has been achieved the patient will enter the second phase of therapy in which they will receive an additional 6 weeks of Campath-1H therapy. The patient will then be reassessed as described above. * No additional therapy (as part of this study) will be performed after a 12 week course of Campath-1H. * While the patient is on Campath-1H blood test will be performed at 3-6 month intervals over a period extending for 2 years following the last treatment. Bone marrow biopsies and/or aspirations will be conducted as necessary.