The exhaust gases composition of a direct propane fuel cell (DPFC) operating at 80 degrees C was studied by mass spectrometric methods. Blank propane was introduced in the anode chamber without external reforming. The effect of the anode catalysts on the composition of the exhaust gases was investigated. It was found that the mass spectra of the electro-oxidized propane presented significant differences compared to the mass spectra of the blank propane introduced directly into the mass spectrometer. It was found that the operation of the DPFC at 80 degrees C involves several processes, i.e., adsorption, dehydrogenation, and C-C bond cleavage of the molecule. It was shown that the intensity of the peaks associated with species like CH4, CO, and C2H4 increases with the polarization potential of the fuel cell. The opposite effect was found for the relative intensity of the molecular ion at m/z = 44, which decreased with the cell polarization potential. These spectrometric characteristics indicate that the composition of the anode exhaust gases is related to the polarization conditions. These results confirm that the direct propane electro-oxidation was responsible for the operation of the DPFC. (c) 2005 The Electrochemical Society.