Graft failure is a life-threatening complication of allogeneic stem cell transplantation (SCT). We assessed the feasibility of performing a second SCT after such failure when fludarabine and antithymocyte globulin (ATG) are used for non-myeloablative conditioning and tacrolimus for graft-versus-host disease (GVHD) prophylaxis. Nine patients with SCTs for various hematologic malignancies were enrolled, eight with primary and one with secondary graft failure. The median time between the first and second SCT was 53 days. Eight patients had the same donor for their second SCT, and one had a cord blood transplant. Three patients were not evaluable because of early death; the other six had evidence of donor cell engraftment. Six of the nine patients developed acute grade II-IV GVHD, the main cause of death. Overall, we found that fludarabine and ATG conditioning before a second SCT allows engraftment of donor hematopoiesis. Future studies should include more intense GVHD prophylaxis.