Fish pre-treated with NAC (1 mmol kg−1, i.p.) and exposed to 1.5 mg l−1 (the 96-h LC85) of dichlorvos for 96 h in a static-renewal system achieved an increase of the GSH content, GSH/GSSG ratio, hepatic glutathione reductase (GR), glutathione S-transferase(GST), glutamate:cysteine ligase (GCL), and -glutamyl transferase (GT) activities, which ameliorated the glutathione loss and oxidation, and enzyme inactivation, caused by the OP pesticide.