The performance of cermet anode of protonic ceramic fuel cells with BaZr0.8Y0.2O3-delta (BZY20) electrolyte has not been investigated sufficiently due to problems in ceramic processing and reference electrodes. In this study, the electrode performance of Ni-BZY20 cermet electrode with the BZY20 electrolyte was evaluated. Functionally symmetrical cells with the BZY20 electrolyte and Ni-BZY20 electrodes were fabricated with initial NiO content of 20-70 wt%. It is shown that hydration of BZY20 should be carried out at higher temperature to alleviate compressive stress in the electrolyte induced by chemical expansion of BZY20. IR resistance and electrode resistance of the cells were evaluated by current interruption and AC impedance measurements. The electrode resistance of the Ni-BZY20 anode containing 40-70 wt% NiO was 0.14-0.2 Omega cm(-2) at 600 degrees C, and almost independent on NiO composition. Excellent durability of Ni-BZY20 supporting electrode in fuel cell mode was also demonstrated with La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) cathode. The electrode resistance of the cell showed almost no degradation through the operation at cell voltage of 0.8 V for 2000 h.