In a retrospective single center study, we examined the outcome of induced GVHD in leukemia patients relapsing after allogeneic BMT. Thirty-three adult patients with leukemia (15 AML, 3 ALL, and 15 CML) persisting or relapsing 1-36 months (median, 6) after allogeneic BMT underwent various immune manipulations and consequently developed acute and/or chronic GVHD at our center. Immunotherapies to elicit GVHD comprised chemotherapy followed by PBSC (n = 18), non-myeloablative transplant (n = 2), PBL followed by IFN-alpha (n = 5), PBL alone (n = 3), abrupt cessation of CsA (n = 3), and CsA withdrawal combined with IFN-alpha (n = 2). Twenty-four (72.7%) patients obtained a remission including complete hematological or cytogenetic remission, respectively, for acute leukemias or CML. Overall survival of patients, estimated at 3 years using the Kaplan-Meier method, was 33.9% (95% CI, 20-52%). Twelve patients including two patients with ALL remain in complete hematological (n = 5) or cytogenetic remission (n = 7) 3-93 months (median 12) after achieving remission. Twelve (63.2%) of 19 dead patients died due to treatment-related toxicities; five patients from acute GVHD, three from GVHD followed by infections and four from infections. By multivariate Cox analysis, only chronic GVHD resulted in a higher probability of disease-free survival (P = 0.026). Eight patients who had both acute GVHD < or = grade I and chronic GVHD are all alive without leukemia. We conclude that acute GVHD is associated with considerable toxicity while chronic GVHD plays a role in retaining remission in leukemia relapsing after allogeneic BMT.