A device to measure surface oxygen tension of the palpebral conjunctiva (PcjO2) was developed and tested in 12 mongrel dogs subjected to normoxia, hyperoxia, and hypoxia. Intravascular pressure, hemodynamic, and bulk oxygen transport variables were measured simultaneously with PcjO2 and transcutaneous O2 (PtcO2) and CO2 (PtcCO2). PcjO2 closely paralleled PaO2 as the fractional inspired O2 concentration was changed from 0.21 up to 1.0 and down to 0.05; the correlation coefficient, r, was 0.95 for 305 data sets. During hyperoxia there were no significant hemodynamic or bulk O2 transport changes, but during hypoxia, the cardiac output and O2 extraction increased while PaO2, PtcO2 and PcjO2 fell; O2 delivery and O2 consumption were maintained until just before death.