Abstract Glutathione-dependent defense against xenobiotic toxicity is a multifaceted phenomenon that has been well characterized in mammals. In the present study, eels of species Anguilla anguilla were exposed to 15 ppm of the herbicide thiobencarb ( S-4-chlorobenzyl diethylthiocarbamate) for 96 h. Eels exposed to the pesticide were grouped in 24-h intervals according to their time of death, while surviving intoxicated eels constituted another group (live animals). Glutathione content (GSx, GSH, GSSG) was determined in liver and muscle tissues of the dead and live (intoxicated) animals and compared to control values (nonexposed eels). The fish that died before 96 h of exposure were considered susceptible to thiobencarb, while those dead after 96 h and the surviving ones were called resistant. Hepatic glutathione (GSH) content in susceptible eels was lower than that in the control fish, while resistant eels presented GSH levels threefold higher than those of controls. Muscle glutathione levels in dead eels were practically unaffected, but there was a significant decrease in GSH levels in the surviving intoxicated eels. These results indicate that the eels that were able to induce glutathione synthesis in the liver due to the presence of thiobencarb in the medium demonstrated a greater longevity than those who lost glutathione homeostasis.