The transcutaneous partial pressures of carbon dioxide (PtcCO2) and oxygen (PtcO2) were measured with heated electrodes in 18 hemodynamically stable pediatric ICU patients and these data were compared to simultaneously measured arterial oxygen and carbon dioxide tensions. There was a significant degree of correlation (p less than 0.001) between the skin surface CO2 and O2 and their corresponding arterial tensions. These data defined values for PtcCO2 and PtcO2 indices in the pediatric patient without cardiovascular complications as PtcCO2 index = 1.6 +/- 0.2 and the PtcO2 index = 0.84 +/- 0.18 (PtcCO2 index = PtcCO2/PaCO2 and PtcO2 index = PtcO2/PaO2). The authors found the monitoring of skin surface gases a reliable technique to monitor arterial gas tension in hemodynamically stable patients.