Cell and stack life and reliability is one of the biggest issues to realize solid oxide fuel cell (SOFC) power generation systems. The R&D investigation on reliability has been carried out under New Energy Development Organization (NEDO) program by authors. Endurance tests were implemented for tubular type SOFCs, and performance analysis results were compared to post test analysis results. The performance was analyzed by using performance estimation equations developed by CRIEPI and longitudinal increase of cathode overpotential was observed. Comparing to the post test analyzed by AIST, Cr poisoning was also observed at the cathode. These results indicate the adequacy of performance estimation method.Copyright © 2008 by ASME