Despite the knowledge that excess amounts of oxygen in the blood (hyperoxia) can be damaging to preterm infants, there is a wide variation in approaches to oxygen therapy within neonatal intensive care units. This is predominantly determined by institutional or individual practices or preferences and might stem from a lack of understanding of the relative merits and demerits of the different techniques of oxygen monitoring in extremely preterm babies who are different from more mature babies. This article provides the physiological rationale and evidence from recent clinical studies suggesting that keeping the oxygen therapy to an “acceptable” minimum in premature babies does not do any harm and may be even advantageous.