We report a 55-year-old man who showed no change after chemotherapy for chronic myelogenous leukemia-blastic crisis (CML-BC) in 1998. Allo-peripheral blood stem cell transplantation (PBSCT) was then performed and Complete remission (CR) was achieved, but recurrence was seen in 2001. Imatinib administration brought about partial remission (PR) and then a reduced intensity stem cell transplantation (RIST) was performed. The bcr-abl gene disappeared and Ph1 chromosome disappearance was ascertained. CR was thus achieved. There are still no established radical methods of treating CML-BC. Thus, therapy by allograft after the patient has entered hematological remission with imatinib is considered a new way of dealing with cases of CML-BC.