A study of workers exposed to jet fuel propellant 8 (JP-8) was conducted at U.S. Air Force bases and included the evaluation of three biomarkers of exposure: S-benzylmercapturic acid (BMA), S-phenylmercapturic acid (PMA), and (2-methoxyethoxy)acetic acid (MEAA). Postshift urine specimens were collected from various personnel categorized as high (n = 98), moderate (n = 38) and low (n = 61) JP-8 exposure based on work activities. BMA and PMA urinary levels were determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and MEAA urinary levels were determined by gas chromatography-mass spectrometry (GC-MS). The numbers of samples determined as positive for the presence of the BMA biomarker (above the test method's limit of detection [LOD = 0.5 ng/ml]) were 96 (98.0%), 37 (97.4%), and 58 (95.1%) for the high, moderate, and low (control) exposure workgroup categories, respectively. The numbers of samples determined as positive for the presence of the PMA biomarker (LOD = 0.5 ng/ml) were 33 (33.7%), 9 (23.7%), and 12 (19.7%) for the high, moderate, and low exposure categories. The numbers of samples determined as positive for the presence of the MEAA biomarker (LOD = 0.1 μ g/ml) were 92 (93.4%), 13 (34.2%), and 2 (3.3%) for the high, moderate, and low exposure categories. Statistical analysis of the mean levels of the analytes demonstrated MEAA to be the most accurate or appropriate biomarker for JP-8 exposure using urinary concentrations either adjusted or not adjusted for creatinine; mean levels of BMA and PMA were not statistically significant between workgroup categories after adjusting for creatinine.