OUTLINE: Patients receive fludarabine IV over 30 minutes on days -9 to -5, cyclophosphamide IV over 1 hour on day -5, and antithymocyte globulin IV over 10 hours on days -5 to -2. Allogeneic peripheral blood stem cells are infused on day 0. Patients who achieve complete remission (CR) and then relapse or patients who achieve less than a CR before day 60 receive donor leukocyte infusions (DLI) over 30 minutes. DLI are repeated as necessary for persistent disease. Patients are followed at 1, 3, and 6 months, then at 1 and 2 years.