Preterm infants exposed to hyperoxia have abnormal ventilatory responses to hypoxia and hyperoxia. To determine if such responses persist into adulthood, 13 adults who were born very preterm were tested by exposing them to five minutes of isocapnic, isobaric hypoxia and hyperoxia. Age-matched adults who were born at full-term were also tested similarly. The ventilatory response to hypoxia was substantially reduced in adults born preterm. Hyperoxia induced respiratory depression in all controls, but only in eight of the 13 subjects born preterm. These results were possibly due to disrupted chemoreceptor development.