In this study, production of intracellular reactive oxygen species (ROS) and nitric oxide (NO center dot),the activities of nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, superoxide dismutase (SOD) and catalase (CAT) and levels of membrane lipid per oxidation (LPO) in ketoconazole-treated Saccharomyces cerevisiae were investigated in a dose- and time-dependent manner. Hydrogen peroxide, total ROS and hydroxyl radical levels in 150-250 mu M ketoconazole-treated cells were increased with increasing concentrations, which reached 4.30, 4.24 and 2.41 times their controls, respectively. Superoxide anion and NO center dot radical levels increased dose dependently up to the fourth hour and then dropped under the controls at 150-225 mu M, while decreasing continuously at 250 mu M. The highest levels were 2.23 and 3.43 times their controls, respectively. While NADH-NADPH oxidases and SOD activities increased with increasing time at 150-225 mu M, extremely induced initial activities decreased throughout incubation at 250 mu M. CAT activities were increased dose and time-dependently up to the fourth hour and the activity reached 3.57 times the control. The highest LPO level was 2.28 times the control at 250 mu M, because of the oxidative stress. The results showed that although the antioxidant system was effectively triggered, it couldn't prevent S. cerevisiae from ketoconazole-induced oxidative stress. (C) 2016 Elsevier Ltd. All rights reserved.