Adaptive adjustment of inspired oxygen (FIO2), based on a desired percent arterial hemoglobin saturation (SO2) was achieved by on-line bedside control of the oxygen concentration delivered to the neonate. Fourteen infants with bronchopulmonary dysplasia (BW, 860 +/- 80 g; GA, 26 +/- 1 weeks; study age, 41 +/- 8 days) receiving oxygen-air mixtures by hood were studied. The desired range of SO2 from 92 to 96% with a target value of 95% was determined by pulse oximetry and maintained with adjustment of FIO2 using three modes: 1) standard neonatal intensive care protocol with oxygen delivery evaluated at 20 minutes intervals; 2) bedside manual control with FIO2 manipulation every 2 to 5 minutes; and 3) adaptive control with on-line adjustment of FIO2 according to a specifically designed adaptive program. Each study period was of 40 minute duration. SO2 values within a steady 94 to 96% range was achieved for 54% of the time with standard protocol, compared to 69% (P less than 0.01) with bedside manual control and 81% (P less than 0.01) with adaptive control. In addition, fluctuations in SO2 values and overshoots were less apparent with adaptive control of oxygen delivery. These data describe adaptive FIO2 control as an efficient alternative technique for achieving a stable desired range of oxygenation in neonates.