Catalytic autothermal reforming of methane and propane over supported metal catalysts has been investigated in the present study. The carbon deposition region and the heat balance of the reaction have been determined from the equilibrium calculations. The sequence of the activities of the 2 wt.% metal on alumina support for autothermal reforming of methane was Rh > Pd > Ni > Pt > Co. The catalytic activity of 10 wt.% Ni/Al2O3 was higher than that of the 2 wt.% Rh/Al2O3. The activity of Ni was significantly lowered by the preferential oxidation of the catalyst in the reactant gas at low temperatures. Although little carbon deposition was observed for the autothermal reforming of methane in the deposition-free region expected from the equilibrium, a large amount of carbon deposition was observed for the propane autothermal reforming even in the steam-rich conditions. The deposited carbon possessed fibrous morphology. The catalytic autothermal reforming appears to be initiated by decomposition of hydrocarbon at the inlet zone; then the reforming reaction subsequently proceeded in the catalyst bed.