OUTLINE: This is a nonrandomized, dose-seeking study. Stem cell donors receive G-CSF for 4 days prior to and throughout stem cell harvest. Patients receive intensive chemotherapy with fludarabine and cyclophosphamide for 3 days, with patients entered at increasing doses of both drugs until the dose allowing engraftment is determined. Three days after intensive chemotherapy, allogeneic stem cells are infused. Responding patients who do not experience worse than grade 1 acute graft-vs.-host disease receive additional stem cell infusions after 60 and 120 days. Patients are followed monthly for 4 months, at 6 and 12 months, then yearly for 5 years.