The rate of carbon dioxide production (VCO2), heart rate, and oxygen saturation were recorded during resuscitation in 30 newborn infants. Twenty eight infants were ventilated through a facemask only and two were intubated after initial facemask ventilation. Five neonates were born at full term, eight had a gestational age of 32-36 weeks, and 17 of 27-31 weeks. Towards the end of the five minute study period, the VCO2 in ventilated infants, born after 32 weeks or more, was not different from that of spontaneously breathing infants. Neonates with a gestational age of 27-31 weeks showed a low VCO2, particularly when no reflex response from the baby was recorded, with a significant increase if a reflex response was elicited. Ventilation was found to be satisfactory if the heart rate increased to 130 beats/min or more within 5-15 seconds or if the oxygen saturation, measured in the right hand, was 70% or more.