A method for estimation of the cutaneous blood flow in transcutaneous PO2 measurements is presented. Recordings of electrode and skin temperature make it possible to compute the effect dissipated to the circulating blood. Eighteen measurements were performed on three healthy volunteers at electrode temperature settings from 37.0 degrees C to 45.0 degrees C. The blood-flow estimates ranged from 0.07 to 0.19 ml . cm-2 . min-1. At an electrode temperature of 45.0 degrees C the investigations showed a tc-PO2 value as low as 7 mmHg (0.9 kPa) which, however, corresponded well to the lowest blood-flow estimate determined. The temperature-corrected (37 degrees C) a-PO2-tc-PO2 gradient ranged from 50 mmHg to 95 mmHg (6.7-12.6 kPa). The investigations confirm the importance of simultaneous determinations of cutaneous blood flow, capillary temperature and cutaneous oxygen consumption in order to describe the connection between arterial and cutaneous oxygen tension. The cutaneous blood flow seems in this connection to be the most important parameter.