The possible artefacts in transcutaneous oxygen tension (tcPO2) induced by fluctuations in arterial blood pressure were investigated in ten newborn babies. We mounted one tcPO2 electrode on the foot and another on the chest, and the local arterial blood pressure under the foot electrode was reduced 0.6-2.0 kPa (9-15 mmHg) by elevating the foot 11-19 cm above the heart level. In five mature newborns the tcPO2 of the foot decreased significantly (p = 0.015) during elevation by a mean valve of 0.029 kPa (0.22 mmHg) per mmHg decrease in mean arterial blood pressure. In five premature newborns the artefact was insignificant (p = 0.62). We conclude therefore that, in contrast to adults, the artefacts induced by minor fluctuations in arterial blood pressure in newborns are hardly of clinical importance.