The value of continuous transcutaneous oxygen (PtcO2) monitoring in the presence of halothane and nitrous oxide (N2O) was studied in 10 infants. All infants were continuously monitored during the study with a Clark-type skin electrode with Mylar membrane. The polarization voltage of the membrane was changed to 600 mV to make it insensitive to N2O and halothane. The accuracy of PtcO2electrode was compared with simultaneously measured PaO2at different intervals. Correlation of PaO2with PtcO2was sought during hypoxic-normoxic state (PaO2between 27–92 torr) and hyperoxic state (PaO2between 105–439 torr). During hypoxic-normoxic state, the correlation between PaO2and PtcO2values was 0.94. During the hyperoxic state, poor correlation existed between PaO2and PtcO2(r = 0.51). Although PtcO2did not correlate with PaO2during hyperoxia, it consistently overestimated PaO2and thereby, provided a predictive ability by over-diagnosing hyperoxia. When combined with continuous monitoring of inspired oxygen tension to maintain normoxia, continuous monitoring of PtcO2will reduce the frequency of PaO2analysis and improve patient care during anesthesia.