The introduction of oxygen into the atmosphere of the earth was a double-edged sword. It provided a source of energy that had allowed the evolution of complex organisms. But it also has the ability to form reactive oxygen species (ROS), which are highly potent oxidants. Oxygen toxicity results from the harmful effects of breathing molecular oxygen at increased partial pressure. Within the cell, ROS can cause genetic degeneration and physiological dysfunction, eventually leading to cell death. Severe cases can lead to deleterious consequences such as multiorgan dysfunction and death. Oxygen is an indispensable part of the therapeutic armamentarium of clinicians. However, the inappropriate and injudicious use of this gas can lead to various toxic manifestations. The concentration of the gas and its duration of exposure are the factors that determine the onset and degree of toxicity. It has been observed that there are marked variations in individual susceptibility. The management of the condition is primarily symptomatic. As there is no specific therapy for oxygen toxicity, prevention remains the cornerstone of management.