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Spermatozoa generate reactive oxygen species (ROS) in physiological amounts, which play a role in sperm functions during sperm capacitation, acrosome reaction (AR), and oocyte fusion. in addition, damaged sperm are likely to be the source of ROS. The most important ROS produced by human sperm are hydrogen peroxide, superoxide anion and hydroxyl radicals. Besides, human seminal plasma and sperm possess an antioxidant system to scavenge ROS and prevent ROS related cellular damage. Under normal circumstances, there is an appropriate balance between oxidants and antioxidants. A shift in the levels of ROS towards pro-oxidants in semen can induce oxidative stress (OS) on spermatozoa. Male infertility is associated with increased ROS and decreased total antioxidant activity in the seminal plasma. ROS induce nuclear DNA strand breaks. Besides, due to a high polyunsaturated fatty acid content human sperm plasma membranes are highly sensitive to ROS induced lipid peroxidation thus decreasing membrane fluidity. This will result in increased lipid peroxidation (LPO), decreased sperm motility, viability, function and ultimately lead to infertility. The protective action of antioxidants against the deleterious effect of ROS on cellular lipids, proteins and DNA has been supported by several scientific studies. The purpose of the present review is to address the possible relationship between ROS and antioxidants production in seminal plasma, and the role they may play in influencing the outcome of assisted reproductive technology (ART). [ABSTRACT FROM AUTHOR]