Multidrug resistance-1 (MDR-1) gene single nucleotide polymorphisms (SNPs) have been identified as associated with the treatment outcomes of acute myeloid leukemia (AML) in Caucasians; yet, similar evidence is lacking for Asian populations. A total of 101 AML patients were enrolled in the current study. Two MDR1 SNPs (C3435T and G2677T/A) were analyzed with PCR/RFLP assay. As regards C3435T polymorphism, C/C genotype was significantly correlated with lower functional P-glycoprotein (P-gp) activity in leukemic blasts (7.5%) compared with C/T (10.7%) or T/T genotype (19.9%, p = 0.029). In genotypic analyses, C/C at −3435 (p = 0.05) and G/G at −2677 (p = 0.04) were strongly associated with a higher probability of complete remission (CR). In addition, the 3-year event-free survival (EFS) was higher in G/G genotype at −2677 (60.6%) than nonG/G (21.9%; p = 0.0241), in C/C at −3435 was higher than nonC/C genotype (p = 0.0139), and was higher in GC haplotype homozygote (58.2%) than nonGC homozygote (22.6%; p = 0.0427). In a multivariate analysis, the group without GC haplotype showed worse EFS (p = 0.030), with unfavorable cytogenetic risk (p = 0.008). However, no differences were noted in overall survival according to the MDR1 SNPs (p = 0.491 for C3435T and p = 0.955 for G2677T/A). © 2005 Wiley-Liss, Inc.