Oxygen is one of the most used, and misused, therapies delivered to critically ill patients.  In recent years, a number of trials have compared the use of a conservative oxygen therapy strategy with a liberal oxygen therapy strategy.  These trials have produced mixed results and the optimal oxygen strategy for critically ill patients remains unknown.  In this podcast, we discuss the latest study, UK-ROX Trial, to investigate a conservative oxygen therapy strategy with usual oxygen therapy in critically ill ICU patients.  Which approach is better?