A dynamic model of oxygen transport through the outer skin layers and a polarographic sensor was developed for the analysis of transcutaneous oxygen tension (tcPO2). It provides a basis for quantifying the factors that determine the relationship between tcPO2 and arterial oxygen tension (PaO2). Model simulations show the importance of stratum papillare metabolic oxygen consumption; the oxygen permeability of the skin relative to that of the sensor membrane and electrolyte; and temperature and the oxyhemoglobin dissociation curve. These simulations were consistent with experimental data obtained by using microcathode transcutaneous oxygen sensors, which were placed on the skin of 10 healthy adults. Furthermore, the model indicates that accurate evaluation of arterial oxygen tension by using transcutaneous measurements requires continuous estimation of skin perfusion. On the basis of tcPO2 measurements made during arterial occlusion, simulations indicate that quantitative evaluation of the metabolic oxygen consumption of the viable skin tissues is possible only when the oxygen permeabilities of the skin and sensor are known.