Objective: To test the hypothesis that preterm infants randomized to a low vs high O2 saturation target range have a higher incidence of intermittent hypoxemia. Study design: A subcohort of 115 preterm infants with high resolution pulse oximetry enrolled in the Surfactant, Positive Pressure, and Oxygenation Randomized Trial were randomized to low (85%-89%) or high (91%-95%) O2 saturation target ranges. Oxygen saturation was monitored until 36 weeks postmenstrual age or until the infant was breathing room air without respiratory support for ≥72 hours. Results: The low target O2 saturation group had a higher rate of intermittent hypoxemia (≤80% for ≥10 seconds and ≤3 minutes) prior to 12 days and beyond 57 days of life (P <.05). The duration shortened (P <.0001) and the severity increased (P <.0001) with increasing postnatal age with no differences between target saturation groups. The higher rate of intermittent hypoxemia events in the low target group was associated with a time interval between events of <1 minute. Conclusion: A low O2 saturation target was associated with an increased rate of intermittent hypoxemia events that was dependent on postnatal age. The duration and severity of events was comparable between target groups. Further investigation is needed to assess the role of intermittent hypoxemia and their timing on neonatal morbidity. Copyright © 2012 Mosby Inc. All rights reserved.