The present study directly compared the effects of exposure to Cr 6+ and Cr 3+ (10mg/L) over 24, 48 and 96h on indices of oxidative stress and activities of antioxidant and related enzymes in goldfish brain, liver, kidney and gills. Glutathione status clearly demonstrated the development of oxidative stress, whereas changes in protein carbonyls and lipid peroxides were less pronounced. The activity of superoxide dismutase (SOD) was virtually unaffected after 24 or 96h exposure, but 48h exposure to Cr 6+ reduced SOD activity in brain (by 30%), enhanced activity in kidney (by 28%) and had no effect on liver SOD. Chromium exposure for shorter times had no effect on catalase activity, whereas 96h exposure depressed activity in liver, kidney and gills. Exposure to Cr 6+ reduced catalase activity in liver by 53% and in kidney by 21%, while in gills it was reduced by 20 and 38% by exposure to Cr 3+ and Cr 6+ , respectively. Exposure to chromium for 24h did not affect glutathione-S-transferase activity, but treatment with Cr 6+ for 48h enhanced it in brain by 1.5-fold, whereas exposure to Cr 3+ decreased activity by 29% in kidney. Fish treatment with chromium ions for 96h decreased glutathione-S-transferase activity in liver by 51 and 25%, respectively. Chromium exposure had very little effect on the activities of GR or G6PDH. These data show that both chromium ions induced oxidative stress in goldfish tissues and affected the activity of antioxidant and associated enzymes.