Primary graft failure after allogeneic hematopoietic cell transplantation is a life-threatening complication. A shortened conditioning regimen may reduce the risk of infection and increase the chance of survival. Here, we report the outcome of 11 patients with hematologic diseases (median age, 44; range, 25-67 years, seven males) who received a 1-day reduced-intensity preparative regimen given as a re-transplantation for primary graft failure. The salvage regimen consisted of fludarabine, cyclophosphamide, alemtuzumab and TBI, all administered 1 day before re-transplantation. All patients received T-cell replete PBSCs from the same or a different haploidentical donor (n=10) or from the same matched sibling donor (n=1). Neutrophil counts promptly increased to >500/μL for 10 of the 11 patients at a median of 13 days. Of these, none developed grade III/IV acute GVHD. At present, 8 of the 11 patients are alive with a median follow-up of 11.2 months from re-transplantation and 5 of the 8 are in remission. In conclusion, this series suggests that our 1-day preparative regimen is feasible, leads to successful engraftment in a high proportion of patients, and is appropriate for patients requiring immediate re-transplantation after primary graft failure following reduced-intensity transplantation.