Four patients with Philadelphia chromosome (Ph1)-positive chronic granulocytic leukemia (CGL) in blast phase received cyclophosphamide, total body irradiation, and autologous marrow transplants using cryopreserved marrow from the stable phase. Two patients fully reestablished stable-phase leukemia that lasted for 26 and six months; the first patient developed transient Ph1-negative hematopoiesis after transplantation. Three patients eventually died of recurrent blast-phase leukemia. Previous studies using autologous marrow for CGL have reported an occasional long survivor, but incomplete engraftment and especially the rapid recurrence of blast-phase leukemia have been responsible for the overall poor results. The latter problem complicates even normal marrow transplantation, indicating the inadequacy of the current therapeutic regimens used for treating blast-phase leukemia and the possibility of improving results with more effective regimens and autologous marrow transplantation. Although it is unknown whether the reestablishment of Ph1-negative hematopoiesis after transplantation contributes to improved survival, this interesting phenomenon must be investigated further.