A 44-year-old woman with AML, while receiving a conditioning treatment with BU-CY for an allogeneic sibling transplant, developed septic shock with pulmonary embolism and heart failure. Conditioning was stopped at the end of the busulfan course and cyclophosphamide omitted. After antibiotics, dopamine and steroids the patient was allografted, using the donor's G-CSF-primed PBSC. She recovered her peripheral blood counts promptly and developed an acute GVHD grade II that responded to steroids. The DNA microsatellite analysis showed full donor engraftment up to a year from transplantation. This case suggests that the use of PBSC may facilitate engraftment in the absence of an effective immunosuppression during conditioning.