Few reports have focused on adolescent and young adult (AYA) patients with acute myeloid leukemia (AML) treated with hematopoietic stem cell transplantation (HSCT). We performed a retrospective analysis based on data obtained from a Japanese nationwide registration database to compare HSCT outcomes in AYA patients with AML with those in children with AML. An analysis of the 2973 patients with de novo AML who received allogeneic HSCT from 1990 to 2013 showed inferior 5-year overall survival (OS) (54% versus 58%, P<.01) and increased treatment-related mortality (TRM) (16% versus 13%, P=.02) in AYA patients. Multivariate analysis for both OS and TRM showed a significant negative impact on AYAs. However, the negative impact of older age lost its significance in an additional analysis focusing on 1407 recent transplant recipients with high-resolution HLA typing (2000 to 2013). Finally, we analyzed the impact of transplantation center type on HSCI' outcomes in 317 adolescent patients (15 to 18 years old) and found no difference in outcomes between patients treated at a pediatric or an adult hospital. Higher age was a strong predictive factor for inferior OS resulting from increased TRM, which can be eliminated with better donor selection using high-resolution HLA typing. (C) 2017 American Society for Blood and Marrow Transplantation.