Transcutaneous measurement of the arterial PO2 is a practicable method for clinical routine work. The covering, calibration and placing of the electrodes are simple. If the circulation is normal, there is a strong correlation between the arterial and transcutaneous PO2. The stability of the electrode permits its employment for long-term monitoring. Recalibration is necessary every 12 h. Comparison with blood gas analysis is essential for control. After measuring for 5-6 h, blistering under the electrode may occur. The electrode has to be re-applied every 4 h. Continuous measurement offers new possibilities in treatment and diagnosis.