The tracks of oxygen transport around platinum or gold electrode/yttria stabilized zirconia (YSZ) electrolyte interface were visualized by oxygen isotope (O-18) labeling (T=773-973 K, p(O-2)=7 kPa, cathodic polarization E=0 or -0.3 V) and multi dimensional imaging using secondary ion mass spectrometry (SIMS). The activation of oxygen exchange reaction was clearly observed as a strong O-18(-) intensity at metal/ YSZ interface treated at T=973 K indicating that the reaction dominantly occurs at gas/electrode/electrolyte triple phase boundary (TPB). Platinum/YSZ interface exhibited a stronger O-18(-) intensity than gold/YSZ, however, the intensity distribution was not homogenous. The effect of applying cathodic polarization on the oxygen transport was more clearly observed at gold/YSZ interface than platinum/YSZ. The cause of differences in experimental results is discussed in connection with the different reaction controlling process among the two electrodes materials. (C) 2008 Elsevier B.V. All rights reserved.