This study measures a whole series of biological endpoints, and histopathological and behavioral changes of carp (Cyprinus carpio L.) fingerlings in order to investigate the adverse effects of a sublethal concentration of 10 mu g/L cyfluthrin for 48 h and one week using the semi-static test system. The most significantly altered findings of this study was that total antioxidant status levels decreased in 48 h, chloride levels decreased in one week, and sodium and phosphorous levels increased in the 48 h-exposed group. Plasma cortisol increased in both the 48 h-exposed and the one-week-exposed groups. The unique tissue was the brain that had an increased level of malondialdehyde after one week of exposure. Such biomarkers may be used in assessing adverse/toxic effects of pesticides as environmental stressors. Potential oxidative-stress-inducing effect of synthetic pyrethroid cyfluthrin, as lipid peroxidation, in addition to its sodium channel blocking, is reported for the first time as an additional mechanism of action. (C) 2009 Elsevier Inc. All rights reserved.