Stationary and spatially oscillating temperature fronts separating regions with high and low temperatures (amplitudes up to 120 K) formed during the atmospheric oxidation of carbon monoxide on a Pd on alumina ring kept in a mixed reactor. The sharp fronts bounded either one or two low temperature regions. The transition from stationary to spatially oscillating fronts occurred at a feed CO/O-2 concentration ratio close to 2.0 and was independent of the reactor temperature. The net rate of local heat generation on the ring was nonuniform leading to angular variation of the temperature of the ignited state, Front motions were affected by both the nonuniformity of the system and the interaction between the catalyst and the ambient gas, The two fronts bounding a low temperature region usually moved at different velocities and their velocities increased with increasing oxygen concentration. In most cases the two fronts did not move in phase, but sometimes they moved in tandem generating a back-and-forth pulse motion. The spatial amplitude of the oscillations decreased as the slope of the net heat generation activity became steeper. The spatial variation of the standard deviation of the temperature was helpful in assessing the dynamics of the oscillating fronts.