The aim of our investigation was to determine the effects of seven cyanobacterial metabolites microcystin-LR (MC-LR), anabaenopeptin-A (ANA-A), cylindrospermopsin (CYL), anabaenopeptin-B (ANA-B) aeruginosin 98 A (AER-A), aeruginosin 98B (AER-B), microginin-FR1 (MG-FR1) and their mixtures on common indicators of oxidative stress in RTgill-W1cells. The cells were exposed to the metabolites at various concentrations and the following parameters were determined after 48 h: catalase (CAT) activity, lipid peroxidation (LPO), total nitric oxide (NO) level and superoxide (SOD) dismutase activity. Data were analyzed with the use of one-way ANOVA (N = 3) and Dunnett's test. We found that all single tested metabolites increased but CYL decreased CAT activity. Mixtures had stimulatory effect, however antagonistic interactions were found in the binary and ternary mixtures. No lipid peroxidation occurred in the cells exposed to any of the tested variant. Only AER-A increased NO level, however the rest of both single metabolites at highest concentrations (1004 nM) and mixtures reduced the level of this parameter. Only ANA-B inhibited SOD activity at the highest concentration, however no alterations were found in the cells exposed to binary or ternary mixtures. The study showed that cyanobacterial metabolites may induce oxidative stress in fish gill cells, however effects are dependent on type of a metabolite and concentration of a component in mixtures. On the basis of antagonistic interactions in ternary mixture it may be hypothesized that during natural exposure components of mixtures may reciprocally mitigate their effects.