We investigated the association between GSTM1 or GSTT1 polymorphisms and clinical outcomes in 133 younger patients with AML of intermediate-risk cytogenetics. Clinical outcomes were not significantly different among the GSTM1 polymorphism genotypes, whereas cumulative incidence of relapse (CIR) was significantly lower and event-free survival (EFS) was significantly higher in patients with the GSTT1-present genotype compared with those with the GSTT1-null genotype (CIR at 5 year, 28.9% vs. 44.6%, P=0.018; EFS at 5 year, 51.4% vs. 34.1%, P=0.029). Our results suggest that GSTT1 gene polymorphism has significant clinical implications in younger patients with AML of intermediate-risk cytogenetics.