Oxygen consumption (VO2) is a sensitive and reliable indicator of any disturbances of thermoregulatory adaptation in the newborn. This study has been carried out in a attempt to find out, if there is any difference between the thermoregulatory processes of healthy and resuscitated neonates. To this end, both VO2 and rectal temperature (RT) were continuously measured in 31 healthy and 13 resuscitated neonates respectively, within the first 140 postnatal minutes and during 30 minutes from the second until the fifth day of their lives. In the healthy neonates, the VO2 used to decrease over the study period. The high initial VO2 observed postnatally is due to mechanisms of thermoregulation beginning immediately after delivery as soon as the newborn child is exposed to chilly environmental temperatures. The brown adipose tissue (BAT) is supposed to be the essential site of non-shivering thermogenesis (NST). The thermogenetic function of this tissue may be shown by local measuring of temperature. In the resuscitated neonates, VO2 was lower than in the healthy children. Hypoxia results in an ineffective capillary blood supply of the BAT owing to a redistribution of circulating blood volume, thus leading to a disturbance of thermoregulation. Since the activity of the BAT is dependent on oxygen supply hypoxia might be regarded as the limiting factor. In the presence of an isothermal environment, the RT measured in the healthy children differed from those determined in the resuscitated neonates. This clearly shows that thermoregulatory processes may be impaired by a difficult birth.(ABSTRACT TRUNCATED AT 250 WORDS)