background. Vancomycin-resistant Enterococcus (VRE) bloodstream infections (BSIs) are associated with increased morbidity and mortality. objective. To determine the hospital costs and length of stay attributable to VRE BSI and vancomycin-sensitive Enterococcus (VSE) BSI and the independent effect of vancomycin resistance on hospital costs. methods. A retrospective cohort study was conducted of 21,154 nonsurgical patients admitted to an academic medical center during the period from 2002 through 2003. Using administrative data, attributable hospital costs (adjusted for inflation to 2007 US dollars) and length of stay were estimated with multivariate generalized least-squares (GLS) models and propensity score-matched pairs. results. The cohort included 94 patients with VRE BSI and 182 patients with VSE BSI. After adjustment for demographics, comorbidities, procedures, nonenterococcal BSI, and early mortality, the costs attributable to VRE BSI were $4,479 (95% confidence interval [CI], $3,500-$5,732) in the standard GLS model and $4,036 (95% CI, $3,170-$5,140) in the propensity score-weighted GLS model, and the costs attributable to VSE BSI were $2,250 (95% CI, $1,758-$2,880) in the standard GLS model and $2,023 (95% CI, $1,588-$2,575) in the propensity score-weighted GLS model. The median values of the difference in costs between matched pairs were $9,949 (95% CI, $1,579-$24,693) for VRE BSI and $5,282 (95% CI, $2,042-$8,043) for VSE BSI. The costs attributable to vancomycin resistance were $1,713 (95% CI, $1,338-$2,192) in the standard GLS model and $1,546 (95% CI, $1,214-$1,968) in the propensity score-weighted GLS model. Depending on the statistical method used, attributable length of stay estimates ranged from 2.2 to 3.5 days for patients with VRE BSI and from 1.1 to 2.2 days for patients with VSE BSI. conclusions. VRE BSI and VSE BSI were independently associated with increased hospital costs and increased length of stay. Vancomycin resistance was associated with increased costs.