A real-time Fourier transform infrared spectroscopy (FTIRS) analysts of the products of methanol oxidation in a prototype direct-methanol fuel cell operating at high temperatures (150 to 185 degrees C) is reported here. The methanol oxidation products on platinum black and platinum-ruthenium catalyst surfaces were determined as a function of the fuel cell operating temperature, current density, and methanol/water mole ratio. Neither formaldehyde nor formic acid was detected in anode exhaust gas at all cell operating conditions. The product distributions of methanol oxidation obtained by on-line FTIRS are consistent with our previous results obtained by on-line mass spectroscopy under similar conditions. With pure methanol in anode feed, methanaldimethylacetal was found to be the main product, methyl formate and CO2 were also found. However, when water was present in the anode feed, the main product was CO2, and the formation of methanaldimethylacetal and methyl formate decreased significantly with increase of the water/methanol mole ratio. increase of cell operating temperature enhanced the formation of CO2 and decreased the formation of methanaldimethslacetal and methyl formate. Pt/Ru catalyst is more active for methanol oxidation and has a higher selectivity toward CO2 formation than Pt-black. Nearly complete methanol oxidation, i.e., the product was almost exclusively CO2, was achieved using a Pt/Ru catalyst and a water/methanol mole ratio of 2 or higher in the anode feed at a temperature of 185 degrees C or above.