The aim of this study was to compare the effectiveness of antioxidants including cysteamine (2.5, 7.5mm), hyaluronan (0.25, 1mgml(-1)) and fetuin (5, 10mgml(-1)) in the freezing of Brown Swiss bull semen. The best percentages of CASA motilities were achieved with 10mgml(-1) of fetuin and 2.5mm of cysteamine. For sperm morphology, 10mgml(-1) of fetuin and 2.5mm of cysteamine had better protective effects (P<0.001). The results of hypo-osmotic swelling test showed that the percentage values of membrane integrity in all the groups, excluding that supplemented with 5mgml(-1) of fetuin, were higher than those of the control group (P<0.001). Results obtained for the DNA damage of sperm cells demonstrated that 0.25mgml(-1) of hyaluronan, and 2.5 and 7.5mm of cysteamine led to lower rates of spermatozoa with damaged DNA, compared with the control group (P<0.001). The maintenance of superoxide dismutase and glutathione peroxidase antioxidant activities following freeze-thawing with 2.5 and 7.5mm of cysteamine and 10mgml(-1) of fetuin was demonstrated to be at a higher level in comparison with the control group (P<0.001). Malondialdehyde formation was found to be lower in the groups supplemented with 0.25mgml(-1) of hyaluronan and 7.5mm of cysteamine after the freeze-thawing process (P<0.001).