Individual serum or plasma bile acid concentrations were measured by high performance liquid chromatography in two groups of workers with differing exposures: to hexachlorobutadiene (HCBD) and a mixture of other chlorinated solvents (SOLVENT) in study A; and trichloroethylene (TCE) in study B. Exposures to HCBD and TCE were associated with highly significant increases in a number of individual and summed bile acid measures, with a dose effect relation shown for HCBD. Exposure to SOLVENT was associated with significant decreases in three bile acid measures but this may have been due to misclassification of exposure. No association was found between any of the exposures and any of the standard tests of liver function. This preliminary study suggests that some chlorinated hydrocarbons are associated with raised bile acid concentrations in the blood of exposed workers. It may be that the changes in such concentrations reflect early and small disturbances of liver function. The significance and mechanism of the changes are yet to be determined.