Recently, residual pharmaceuticals are generally recognized as relevant sources of aquatic environmental pollutants. However, the toxicological effects of these contaminants have not been adequately researched. In this study, the chronic toxic effect of carbamazepine (CBZ), an anticonvulsant drug commonly present in surface and ground water, on hepatic antioxidant status and hematological parameters of rainbow trout were investigated. Fish were exposed at sublethal concentrations of CBZ (1.0mug/l, 0.2mg/l and 2.0mg/l) for 7, 21 and 42 days. Compared to the control group, fish exposed at higher concentration (0.2mg/l or 2.0mg/l) of CBZ showed significantly higher levels of hemoglobin, ammonia and glucose, and significantly higher plasma enzymes activities. During the exposure duration, erythrocyte count, hematocrit, mean erythrocyte hemoglobin, mean erythrocyte volume, mean color concentration and total protein content in all groups were not significantly different. At the highest test concentration (2.0mg/l) of CBZ, oxidative stress was apparent as reflected by the significant higher lipid peroxidation and protein carbonyl levels in liver after 42 days exposure, associated with an inability to induce antioxidant enzymes activities including superoxide dismutase, glutathione peroxidase and glutathione reductase. After 42 days exposure, reduced glutathione level was significantly decreased in the fish exposed at 0.2mg/l CBZ, compared with the control. In short, CBZ-induced physiological and biochemical responses in fish were reflected in the oxidant stress indices and hematological parameters. These results suggest that hepatic antioxidant responses and hematological parameter could be used as potential biomarkers for monitoring residual pharmaceuticals present in aquatic environment.