In order to investigate the advantages and shortcomings of two application techniques proposed for the tcPCO2 electrode in the fetus we performed a trial using two electrodes with different modes of fixation synchronously. Comparing the transcutaneously measured values with the values of the fetal blood we found a statistically significant correlation for both techniques (r = 0.83 and 0.80, respectively). The mean values of the tcPCO2 though were significantly higher when the suction fixation was used compared with the glue fixation.