In this study, we report the change of semen superoxide dismutase (SOD) and acrosin activities in the male sterility patients with positive antisperm antibody (AsAb). The activity of SOD was measured by xanthine oxidase assay and sperm acrosin activity was calculated by BAEE/ADH. Our data show that compared with the normal fertility group, the semen SOD activity in AsAb-positive patients was significantly lower. Similarly, the sperm acrosin activity in AsAb-positive patients was also significantly lower. Our results suggest that the sterility resulting from positive AsAb may be related with the changes of semen SOD and sperm acrosin activities.