The ability of ethanol to alter glutathione (GSH) conjugation and its dependence upon duration of administration were investigated in rats in correlation with lipid peroxidation and the induction of microsomal enzymes. Significant decreases in hepatic GSH and glutathione-S-transferase (GST) activity in both liver and lung were found in rats treated acutely with ethanol (4 g/kg body weight 6 hr prior to killing). These decreases were accompanied by an increased loss of both GSH and GST into the plasma and increased hepatic lipid peroxidation. On the other hand, there was a dose-dependent increase in hepatic GSH after chronic administration of ethanol in drinking water (5 and 10%) for 3 weeks. This increase in hepatic GSH may be due to increased synthesis of GSH in the liver. No significant induction of GST by chronic ethanol treatment was observed in either organ. Ethanol was compared with the well-known inducers phenobarbital and beta-naphthoflavone. Although there was some evidence of increases in lipid peroxidation and/or microsomal enzyme activity with the inducers, no simple link between these increases and the induction of GST activity was identified.