The efficacy of salvage interferon-α (IFN-α) treatment was investigated in patients with unsatisfactory response to minimal residual disease (MRD)-directed donor lymphocyte infusion (DLI) (n =24).Patients who did not become MRD-negative at 1 month after DLI were those with unsatisfactory response and were eligible to receive salvage IFN-α treatment within 3 months of DLI.Recombinant human IFN-α-2b injections were subcutaneously administered 2-3 times a week for 6 months.Nine (37.5％),6 (25.0％),and 3 (12.5％) patients became MRD-negative at 1,2,and ＞ 2 months after the salvage IFN-α treatment,respectively.Two-year cumulative incidences of relapse and non-relapse mortality were 35.9％ and 8.3％,respectively.Two-year probabilities of event-free survival,disease-free survival,and overall survival were 51.6％,54.3％,and 68.0％,respectively.Outcomes of patients subjected to salvage IFN-α treatment after DLI were significantly better than those with persistent MRD without IFN-α treatment.Moreover,clinical outcomes were comparable between the salvage DLI and IFN-α treatment groups.Thus,salvage IFN-α treatment may help improve the outcome of patients with unsatisfactory responses to MRD-directed DLI and could be a potential salvage treatment for these patients after allogeneic hematopoietic stem cell transplantation.