The impact of single nucleotide polymorphisms of two loci (C3435T and G2677T/A) of the multidrug resistance-1 gene (MDR1) was investigated in 82 patients undergoing allogeneic stem cell transplantation (SCT). The GG genotype on G2677T/A loci was associated with higher non-relapse mortality than was the non-GG genotype (67% vs. 32%, p=0.0073), but not the C3435T (p=0.2026) or MDR1 haplotype (p=0.2238). Accordingly, overall survival was significantly correlated with the G2677T/A genotype (p=0.0048). Multivariate analysis also showed that the GG genotype at G2677T/A had an unfavorable prognosis in terms of overall survival (p=0.003) and non-relapse mortality (p=0.031). In conclusion, the G2677T/A genotype seems to be associated with transplantation outcomes, especially non-relapse mortality.