The technical possibility and possible issues of an intermediate–temperature–operated polymer electrolyte fuel cell (@120 °C) is investigated with an eye toward the launching of new fuel cell heavy–duty vehicles on the world market. Commercial perfluorosulfonic acid membrane and a commercial Pt catalyst supported on carbon are selected to clarify the possible issues in the fuel cells. The cell resistivity at high humidity is less than 0.1 Ω cm –2 . The mass activity (@ 0.85 V, Pt loading amount: 0.33 mg Pt cm −2 ) approaches 850 A g Pt –1 . The high gas crossover rate through the membrane leads to decreased open circuit voltage, which necessitates the use of higher Pt loadings (>0.30 mg Pt cm –2 ) at the cathode to mitigate the effect of the mixed potential. Pt degradation during 120 °C operation at low humidity is found to be much lower than that during 80 °C operation at high humidity based on the results of load–cycle durability testing.