The authors analyzed the outcome of 349 patients with primary or secondary myelofibrosis undergoing reduced intensity transplantation, of whom 35 had accelerated-phase myelofibrosis. After a median follow-up of 5.9 years, estimated 5-year overall survival was between the two groups, and median overall survival was not reached. In terms of relapse, five-year incidence was 30% for the accelerated-phase group versus 15% for the chronic-phase group. Reduced intensity transplantation showed excellent survival but higher relapse for accelerated-phase myelofibrosis.