The activities of catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), and glutathione-S-transferase (GST) were evaluated in the gills (GI) and digestive gland (DG) of Magallana gigas oysters exposed to tamoxifen (TAM) at environmental concentrations of 10 and 100 ng L- 1 for 1 and 4 days. A higher CAT activity in the GI and DG and higher GPx activ...