The development of graft-versus-host disease (GVHD) in patients undergoing allogeneic bone marrow transplantation for leukemias and lymphomas has been associated with a lower incidence of relapse. This phenomenon is thought to be secondary to the anti-tumor effect of adoptively transferred cells. Cyclosporin A (CsA) therapy is known to cause autologous and syngeneic GVHD in experimental models and humans, and has been used in patients undergoing autologous bone marrow transplantation. It has been the consensus to date that CsA-induced autologous GVHD is generally mild, confined to the skin, self-limiting and non-life-threatening. We report by case of severe and progressive GVHD induced by CsA in a child following autologous bone marrow transplantation for acute lymphoblastic leukemia in second remission.