Certain bile acid oxazoline derivatives (100 microM), but not corresponding unconjugated bile acids (100 microM), were found to inhibit the growth of Eubacterium sp. V.P.I. 12708. The growth inhibition was correlated with the polarity of the steroid portion of the bile acid oxazoline. Primary cultures of adult rat hepatocyte monolayer cultures converted [7 epsilon-14C]methylchenooxazoline3 into MeOH-H2O soluble derivatives. Certain intestinal bacteria were capable of metabolizing [17 epsilon-14C]methylchenooxazoline as well as the MeOH-soluble hepatocyte derivative(s). These results suggest that bile acid oxazoline derivatives may undergo hepatic, as well as bacterial metabolism during enterohepatic circulation.