Heart rate (HR), heart rate variability (HRV), respiratory rate (RR) and transcutaneous PO2 and CO2 of 12 infants born by elective cesarean section were monitored during the first postnatal hour in order to evaluate the effect of the beta-mimetic tocolytic drug ritodrine. Six of the mothers received ritodrine by infusion and the other 6 physiological saline during the 2 h prepartum. The Apgar scores of the treatment group were higher (p less than 0.05) but there was a significant increase in RR (p less than 0.05) during the first hour in these babies. Arterial blood pressure (BP) was lower in the group whose mothers had received ritodrine (p less than 0.05) but there was no difference in pulse pressure. Transcutaneous pressure of CO2 (PtcCO2) of the controls decreased during the first hour (p less than 0.05). Transcutaneous pressure of O2 (PtcO2) increased during the first postnatal hour (p less than 0.01) when both groups were examined together. HR of both groups was relatively high and HRV low.