The purpose of study was to evaluate the effect of stopping use of cyclosporine A (CsA) in reversion of donor chimeras of chronic myeloid leukemia (CML) patients relapsed after transplantation. Two CML patients were transplanted with allogeneic peripheral blood stem cells, and relapsed after transplantation, their bcr/abl gene and/or ph1 chromosome showed positive, donor chimeras decreased. For these two CML patients relapsed after transplantation, the use of CsA was stopped immediately, and the patient's body temperature, skin rash, blood picture, liver function and chimeras were planed to observe carefully. The results indicated that acute graft versus host disease (aGVHD) appeared in both patients. A hundred percent (100%) of donor chimeras were then found with bcr/abl gene and/or ph1 chromosome turning to negative in both patients. In conclusion, to stop using of CsA might be effective in the treatment of some CML patients relapsed after transplantation by reversing of donor chimeras and inducing graft-versus-leukemia (GVL) effect accompanied by GVHD.