**9. Conclusions**

Oxygen toxicity is an inherent double-edged sword to aerobic life. Increased oxidative insults to sperm lipids, proteins and DNA are associated with alterations of signal transduction mechanisms crucial for fertility. The origin of ROS generation and the etiologies of increased ROS in men with low sperm quality are becoming increasingly clear, offering multiple management and/or treatment options. Recent evidence suggests that spermatozoa possess an inherent ability to generate ROS essential for the fertilization process. A variety of defense mechanisms against ROS overproduction encompassing antioxidant enzymes, vitamins and other biologically active molecules are involved in biological systems. A balance of the benefits and risks from free radical production seems to be crucial for the sperm survival and function. As male infertility continues to play an increasing role in contributing to the inability to conceive in couples of reproductive age, it is pivotal for andrologists to fully comprehend the importance of thoroughly evaluating seminal oxidative profiles in order to provide a better care for male patients with reproductive dysfunction. Although the therapeutic use of antioxidants appears attractive, clinicians need to be aware of exaggerated claims of antioxidant benefits by various commercial supplements for fertility purposes until proper multicenter trials have been completed. However, initial data emphasizing on the potential of antioxidant supplementation in improving semen quality and conception rates are indeed encouraging.
