Oxidative stress-related parameters were investigated mainly in hepatic tissue of tilapia exposed for 7 days in Rio do Braço, industrial area of Joinville – SC. Signs of pollution were observed by the use of biomarkers, such as an increase in the liver cytochrome P4501A (CYP1A) and CYP2B immunodetection and decrease in hemoglobin content. An indication of oxidative stress was obtained by the increase in the levels of lipid peroxidation end products in livers and a decrease in the levels of glutathione in liver and blood of animals caged in Rio do Braço. One site (S1) showed increased activity of the antioxidant enzymes glutathione peroxidase, catalase and glutathione reductase, but that of gamma-glutamyl transpeptidase (GGT) decreased. While exposition in the second site, S2, induced far less alterations, when compared to reference site animals. An increase in the levels of oxidized glutathione and a decrease the activity of GGT were the only altered variables, indicating that S2 is a less polluted site. The results show evidence of site-specific contamination load in Rio do Braço. The good agreement between induction of CYP1A/CYP2B and oxidative-related parameters warrants the inclusion of oxidative stress markers in biological monitoring programs, which will give support to interpret the responses of classical biomarkers of aquatic contamination.