Treatment with cyclosporine A, a prototypic immunosuppressive drug, following autologous bone marrow transplantation (autoBMT) induces autologous graft-versus-host disease (autoGvHD), similar to acute GvHD after allogeneic BMT. The development of autoGvHD appears to be associated with the emergence of autoreactive T cells recognizing self MHC class II antigens and the elimination of a T-cell-dependent peripheral autoregulatory mechanism. The induction of autoGvHD may be of benefit to the autoBMT patients by providing the graft-versus-tumor effect.