This paper aims to investigate the effect of H2O2 and paraquat on the activities of superoxide dismutase (SOD) and catalase (CAT). and membrane lipid peroxidation (LPO) levels in newly isolated Streptomyces sp. M3004. SOD activities of Streptomyces sp. M3004, grown in 10 mM and 30 mM H2O2, were significantly lower than the control cultures. On the other hand, as an antioxidant enzyme, CAT activity in both H2O2 treatment conditions increased significantly compared with the control. These activity values in 10 mM and 30 mM H2O2 treatment on the 48th hour of incubation were 3.8- and 6.6-fold higher than the control, respectively. SOD activity decreased significantly with respect to paraquat concentration, which was added at the start of the incubation. CAT activities increased significantly in 1.0 mM and 3.0 mM paraquat treatments compared to control. As an indicative marker of membrane damage, LPO levels of the novel isolate Streptomyces sp. M3004 treated with H2O2 and paraquat stress conditions were significantly higher than the control. Nevertheless, compared with the 30 mM H2O2 in both treatment conditions, LPO levels in 10 mM H2O2 were significantly higher. The decreases in SOD activities in paraquat and H2O2 treatment conditions resulted in the increases in the LPO levels although it increases in CAT activities. (c) 2006 Published by Elsevier Ltd.