Graft-versus-host disease (GVHD) remains a major obstacle to successful bone marrow transplantation. Depletion of T lymphocytes from the donor marrow prior to transplantation substantially reduces the morbidity and mortality due to acute and chronic GVHD. Unfortunately, graft failure, usually due to rejection and leukemia relapse, are adversely affected by this approach. This article reviews current techniques for T-cell depletion and results of recent clinical trials directed to overcome major problem areas.