Multi-institutional randomized phase III trial of a non-myeloablative preparative regimen with fludarabine and busulfex with or without anti-lymphocyte antibodies (monoclonal humanized Campath-1H administered s.c. or polyclonal rabbit anti-T lymphocyte antibodies (ATG), combined with low dose and short course cyclosporine A (CSA) and methotrexate (MTX) as the sole agent for prevention of graft-vs-host disease (GVHD) for patients with acute myelogenous leukemia or myelodysplastic syndrome undergoing allogeneic stem cell transplantation from an HLA compatible donor.