Benzene, toluene, ethylbenzene and xylenes (BTEX) are volatile organics compounds that are commonly found in many solvents and petroleum products. Although BTEX compounds are rapidly metabolized and eliminated in the human body, persistent exposure can result in a measurable internal dose. The National Health and Nutrition Evaluation Survey (NHANES) gathers data on a host of chemicals found in the general public and, as such, are useful for interpreting data gathered during exposure investigations designed to assess whether particular individuals are being exposed to chemicals in their environment. The objective of this investigation was to derive serum reference values for the national population using BTEX serum concentration data (ng/ml) from the 2003-2004 NHANES dataset. Weighted summary statistics were calculated for BTEX serum levels using NHANES subset-specific 2-year weights. Data were evaluated by several demographic variables including gender, age, and ethnicity, as well as by smoking status based on two biomarkers for smoking [2,5-dimethylfuran (DMF) and cotinine]. Consistent with prior analyses of earlier NHANES datasets, data distributions for all compounds were right-skewed. m/p-Xylene (median: 0.13, range: 0.02-5.6) and toluene (0.1, 0.02-9.0) had the highest serum levels, followed by benzene (0.03, 0.02-1.4), o-xylene (0.03, 0.02-1.5), and ethylbenzene (0.03, 0.02-1.6). No significant trends were noted when serum concentrations were evaluated by demographic variables. However, smokers had elevated mean and median serum levels for all compounds except o-xylene regardless of the smoking biomarker. While historically cotinine has been the standard smoking biomarker, DMF is now believed to be a better measure of smoking because it is a direct by-product of tobacco smoke. We found serum BTEX levels in smokers were higher when using DMF as the biomarker for smoking activity regardless of statistic (mean, median, 95th percentile). In conclusion, these summary statistics are useful reference values for investigators assessing exposures to BTEX compounds.