We hypothesized that antenatal exposure to glucocorticoids influences subsequent pulsatile cortisol (F) secretion in premature neonates. To test this hypothesis, blood was sampled for plasma F determinationviaindwelling arterial lines at 15-min intervals for 6 h in 26 clinically stable neonates whose gestational ages were 25-33 wk. Deconvolution analysis was used to characterize F secretion and elimination. Pulsatile F secretion was observed in all neonates. Deconvolution estimates in eight neonates exposed to antenatal glucocorticoids (ANG group) were compared with those of 18 neonates not or only remotely exposed to ANG (No/RG group). The median amplitude of the F secretory burst of the ANG group was significantly less than that of the No/RG group [4.3 nmol/Lv·min and 9.2 nmol/Lv·min, respectively;p= 0.026 (Lvis liter of F distribution volume)]. The number and duration of F secretory bursts was similar for both groups: 5 bursts per 6 h, and 23versus16 min. By univariate linear regression analysis, mean arterial blood pressure correlated positively with F secretory burst frequency and F production rate (p= 0.0035,r= 0.55 andp= 0.0067,r= 0.52, respectively). We propose that ANG treatment modulates the amplitude of pulsatile F secretion in premature neonates.