[en] Bile metabolites were measured in fish collected from the Eastern Cornbelt Plains (ECBP) Ecoregion to determine the distribution and levels of exposure to combustion by-products and petroleum. Bile was collected from the gall bladder of 1 to 6 white suckers from 118 sites across Ohio (107), Indiana (8) and Michigan (3) using a randomized EMAP statistical sampling design. Diluted bile was measured at 380/430 nm to estimate the exposure to BaP-type compounds and 290/335 nm to estimate naphthalene-type compounds. Fixed fluorescence readings were normalized to the concentration of protein in bile. Mean values for all sites had skewed distributions. For BAP the mean, standard deviation, skewness and kurtosis were 129.3, 137.3, 2.7 and 8.5, respectively. The corresponding values for NAPH were 29.1, 19.2, and 4.9 and 34.3. The range for the lowest 10% of sites was from 0 to 24.1 for BAP, and was from 8.5 to 15.8 for NAPH. The range for the highest 10% was from 276.9 to 757.3 for BAP, and was from 45.7 to 181.9 for NAPH. For first order stream sites, the range for the lower 10% and the upper 10% were from 29.2 to 34.2 and from 436 to 757.3 for BAP. The corresponding numbers for NAPH were from 17 to 18.5 and 45.7 to 84.9. For second order stream sites, the above ranges were from 3.5 to 21.9 and from 282.2 to 723.8 for BAP. The corresponding numbers for NAPH were from 8.5 to 14.3 and from 37.6 to 63.4. For the third order stream sites, the lower and upper 10% ranges were from 0 to 22.6 and from 207.1 to 421.8 for BAP. The respective numbers for NAPH were from 12.1 to 15.5 and from 53.6 to 181.9