Abstract. The collagen gel sandwich culture of hepatocytes has been proposed as one of the most suitable culture models available for biotransformation studies of xenobiotics. It is a complex model which imitates the cascade of enzymatic events of in vivo biotransformation and allows investigation of biological endpoints under realistic conditions. The biotransformation of trichloroethylene (TRI) has been studied in this model using rat hepatocytes. Headspace gas chromatographic measurements revealed that hepatocytes, cultured for 4 days in this in vitro system, metabolised TRI into the major oxidative metabolites trichloroacetic acid (TCA) and trichloroethanol (TCE). Cultured hepatocytes were exposed either to TRI, or to TCA and TCE. Endpoints studied were albumin secretion and the cytochrome P450 (CYP)-dependent enzymatic activities ethoxyresorufin O-deethylase (EROD), pentoxyresorufin O-depentylase (PROD) and N-nitrosodimethylamine demethylase (NDMA). The results show that both the parent compound and its metabolites exert specific effects on different CYP-dependent mono-oxygenase activities, as seen in vivo. It is suggested that collagen gel sandwich cultures represent a useful in vitro model for the investigation of metabolism-linked toxicity studies.