A new approach to the determination of energy delivered to the skin during transcutaneous oxygen tension (tc-PO2) measurements was tested. The test was carried out using a tc-PO2 electrode constructed with an active thermal shield in order to provide more sensitive and specific heat transport measurements, and consequently to create the possibility of determining skin blood flow rates. The oxygen measurement properties did not differ from the conventional tc-PO2 electrode. In vivo measurements were performed on 11 adult volunteers. Skin blood flow was determined by a blood flow cessation technique to be 0.124 +/- 0.053 ml . cm-2 . min-1 at the start of the experiments, rising to 0.164 +/- 0.61 ml . cm-2 . min-1. Tc-PO2 changed from 56.2 +/- 9.8 mmHg (7.5 +/- 1.3 kPa) to 68.3 +/- 9.0 mmHg(9.1 +/- 1.2 kPa). It is concluded that a thermally shielded electrode makes it possible to determine the convectional component of the heat loss from the electrode to the skin and consequently to compute a relative measure of skin blood flow rate. The observed change in computed skin blood flow rate was correlated to the observed change in tc-PO2 (P less than 0.1).