The interaction of trichloroethylene (TCEL) and isopropyl alcohol (IPA) was studied in the perfused rat liver. Experiments consisted of four parts; TCEL administration with or without IPA, chloral hydrate (CH) administration with or without IPA, IPA administration with or without CH, IPA administration with or without trichloroethanol (TCE). The chemicals were administered into the perfusate of Krebs-Henseleit buffer saturated with 95%O2/5%CO2 in a non-recirculating circuit. Concentrations of the following three metabolites in the effluent were continuously measured by gas chromatograph and chemical methods: TCE and trichloroacetate (TCA) (metabolites of TCEL and CH), and acetone (a metabolite of IPA). Fluorescence from intracellular reduced pyridine nucleotides (NADH, NADPH) was monitored by surface fluorometry. The results showed that IPA changed the TCA/TCE ratio in the TCEL metabolism because of an increase in NADH production, and IPA oxidation was suppressed by CH because of an inhibitory effect of TCE on alcohol dehydrogenase. It was concluded that IPA and TCEL, both ubiquitous agents, interacted with each other in their metabolic pathways in the perfused rat liver, suggesting a new feature of a combined effect of these chemicals when they coexist.