Stability of the catalyst layer (CL) operation with respect to small temperature disturbance is analyzed. The model includes the non-stationary heat transport equation coupled to the steady-state CL performance model. Dispersion relation of the system shows that for typical operating conditions, the CL operation is stable. Thermal instability caused by the growth of the exchange current density with the temperature can only occur in the case of dramatic reduction of the CL thermal conductivity. This instability should, therefore, be excluded from the list of "suspects" in provoking CL and membrane local degradation. (C) 2010 Elsevier B.V. An rights reserved.