There is no doubt to say that semen analysis is the cornerstone for a male fertility evaluation but there are times when it does not produce accurate results. To overcome such a situation, the ROS, Reactive Oxygen Species test has been introduced. It is one of the latest resources available in the market to detect the presence of free radicals in the sperm. The polyunsaturated fatty acids in the plasma membrane of sperm cells are highly susceptible to damage due to reactive oxygen species. Due to an imbalance in the amount of oxidants and antioxidants in the body, the quality of sperms gets affected and it further affects the ability of sperms to fertilize an egg. Therefore, it is very important and useful to perform ROS test as it is the only way to detect the presence of oxidative stress in the sperms. If a man is suffering from infections, varicoceles or occupational exposure to toxins, even then ROS proves to be a useful test.