Rats were exposed to hexachlorobutadiene (HCBD) or tetrachloroethylene (TET) in order to determine which of these chemicals was more likely to be responsible for elevations in individual serum bile acids (SBA) found in workers exposed primarily to these two chemicals. Increases in cholic and taurocholic acids were found on exposure to high doses of HCBD. Elevations of SBA occurred right down to low exposures for TET, however, with cholic, chenodeoxycholic, and glycocholic acids being the most sensitive bile acids. Only at high doses for each chemical was there any indication of liver injury as determined by routinely used parameters such as serum enzymes or bilirubin. The data suggest that TET is likely to play a role in the elevated individual SBA in an exposure situation where both this chemical and HCBD are found.