Continuous transcutaneous PO2 [oxygen partial pressure] measurements (tcPO2 measurements) were performed in healthy volunteers who were breathing air and O2 under hyperbaric conditions (max. [maximum] 4 ata [atmospheres of absolute pressure]). The results show a close correlation of PO2 values measured by the noninvasive method, in blood from discrete arterial punctures, chamber PO2, respectively, the PO2 of the inspiratory gas mixture which was checked up to maximal values of 2200 mm Hg. The PO2 in the arterial blood samples was measured immediately after the puncture inside the hyperbaric chamber using a specially designed electrode.