Lipopolysaccharide binding protein (LBP) function is dependent on circulating LBP levels. Disturbance of LBP transcription regulation may influence the risk for clinical events. In a nested case-control study using a single nucleotide polymorphism haplotype tagging (tagSNP) approach, we assessed whether genetic variation in the LBP gene influences the risk for Gram-negative (GN) bacteremia after allogeneic hematopoietic cell transplantation (HCT), then validated the association in a prospective cohort by correlating genetic variation with basal serum LBP levels and mortality. Presence of the tagSNP 6878 C allele among patients was associated with a 2-fold higher risk for GN bacteremia (odds ratio = 2.15; 95% confidence interval [CI], 1.31-3.52, P = .002). TagSNP 6878 was in strong linkage disequilibrium with 3 SNPs in the LBP promoter, one of which was SNP 1683 (r(2) = 0.8), located in a CAAT box that regulates LBP promoter efficiency. SNP 1683 was associated with higher median basal serum LBP levels (TT 8.07 microg/mL; TC 10.40 microg/mL; CC 17.39 microg/mL; P = .002), and a 5-fold increase in GN bacteremia related mortality after HCT (hazard ratio = 4.83; 95% CI, 1.38-16.75, P = .013). These data suggest that transcriptional regulation of the LBP gene contributes to the risk for developing GN bacteremia and death after HCT.