Purpose: We previously reported a higher risk of mortality among Hispanics after allogeneic hematopoietic stem-cell transplantation (HSCT). However, it is not known how specific post-transplantation events (acute or chronic graft-versus-host disease [GVHD], treatment-related mortality [TRM], and relapse) may explain mortality differences. The purpose of this study was to examine the relationship between ethnicity and post-transplantation events and determine their net effect on survival. Patients and Methods: We identified 3,028 patients with acute myeloid leukemia, acute lymphoblastic leukemia, or chronic myeloid leukemia reported to the International Bone Marrow Transplant Registry between 1990 and 2000 who received an HLA-identical sibling HSCT after a myeloablative conditioning regimen in the United States. There were 2,418 white patients (80%) and 610 ethnic minority patients (20%), of whom 251 were black (8%), 122 were Asian (4%), and 237 were Hispanic (8%). Cox proportional hazards regression was used to compare outcomes between whites and ethnic minorities while adjusting for other significant clinical factors. Results: No statistically significant differences in the risk of acute or chronic GVHD, TRM, or relapse were found between whites and any ethnic minority group. However, Hispanics had higher risks of treatment failure (death or relapse; relative risk [RR] = 1.30; 95% CI, 1.08 to 1.54; P = .004) and overall mortality (RR = 1.23; 95% CI, 1.03 to 1.47; P = .02). Conclusion: The higher risks of treatment failure and mortality among Hispanics may be the net result of modest but not statistically significant increases in both relapse and TRM and cannot be accounted for by any single transplantation-related complication. Further studies should examine the role of social, economic, and cultural factors.