 OUTLINE: This is a randomized, placebo-controlled, double-blind, multicenter study. Patients are stratified according to prior graft-versus-host disease GVHD prophylaxis immunosuppressive therapy vs T-cell depletion, GVHD organ manifestation skin only vs other, donor type 66 matched sibling vs other, and participating center. Patients are randomized to 1 of 2 treatment arms. 