The short-term outcomes of the BOOST II trials have been published. BOOST II consisted of three international randomized trials of over 2000 infants born before 28 weeks of gestation, in which the effects of targeting an oxygen saturation of 85 to 89%, versus a range of 91 to 95% were compared. The pulse oximeters’ calibration algorithm was revised midway through the study. Interim analysis showed an increased rate of death at 36 weeks in the group with a lower oxygen saturation. Hence the study was stopped early. Among the infants treated with the revised oximeter-calibration algorithm, the rate of death was significantly higher in the lower-target group than in the higher-target group (23% vs. 16%). Among all study infants, those in the lower-target group for oxygen saturation had a reduced rate of retinopathy of prematurity (11% vs. 14%) and an increased rate of necrotizing enterocolitis (10% vs. 8%).