The FAS (TNFRSF6/CD95/APO-1) gene is silenced in many tumor types, resulting in an inability to respond to proapoptotic signals. The FAS promoter is polymorphic, including a G to A substitution at -1377 bp and an A to G substitution at -670 bp, which occur within SP1 and signal transducers and activators of transcription 1 transcription factor binding sites, respectively. In a case-control study of adult acute myeloid leukemia (AML), we show a significantly increased risk of AML associated with heterozygotes (GA) and homozygote variants (AA) at position -1377 bp (32.3% in cases versus 22.0% in controls; odds ratio, 1.69; 95% confidence interval, 1.32-2.16). Extended haplotype analysis revealed that the -1377A/-670A haplotype was significantly associated with disease (3% versus 0.5%; odds ratio, 6.72; 95% confidence interval, 3.13-14.51). These data suggest that variation in the FAS gene promoter may affect FAS gene expression and modulate apoptotic signaling, contributing to an increased risk of AML.