The metabolism of trichloroethene by glutathione conjugation was investigated in rat liver subcellular fractions and in male rats in vivo. In the presence of glutathione, rat liver microsomes transformed [14C]trichloroethene to S-(1,2-dichlorovinyl)glutathione (DCVG) identified by gas chromatography mass spectrometry after hydrolysis to the corresponding cysteine S-conjugate and chemical derivatisation. In bile of rats given 2.2 g/kg trichloroethene. DCVG was present in concentrations of 5 nmol (7 ml bile collected over 9 h) and identified by thermospray mass spectrometry after HPLC-purification. E- and Z-N-acetyl-dichlorovinyl-L-cysteine (3.1 nmol present in the pooled 24-h urine) were identified by GC/MS after methylation and butylation as urinary metabolites of trichloroethene (2.2 g/kg, orally). The presented results demonstrate that glutathione-dependent metabolism of trichloroethene is a minor route in the biotransformation of this haloalkene in rats. Formation of S-(1,2-dichlorovinyl)-glutathione, processing to S-(1,2-dichlorovinyl)-L-cysteine and metabolism of this S-conjugate by cysteine beta-lyase in the kidney to reactive and genotoxic intermediates may account for the nephrocarcinogenicity observed after long time administration of trichloroethene in male rats.