Abstract The kinetics of the CO oxidation reaction on Pt/Al 2O 3as well as Pd/Al 2O 3have been measured in a packed bed reactor heated by microwave energy. The reaction rate was also measured in an identical reactor that was heated via conventional means. Several methods of temperature measurement were explored for the determination of catalyst temperature in the microwave heated reactor. Insertion of a thermocouple after the microwaves have been switched off provided the best method for temperature measurement in this study. However, large-scale temperature gradients must be eliminated before this method can provide accurate temperature measurements. After suitable modifications in our packed bed reactor to eliminate nonisothermality, we found that the rate of reaction and the reaction kinetics (order of reaction) for the microwave heated CO oxidation reaction were comparable to those for the conventionally heated reactor. The CO oxidation reaction therefore serves as an in situprobe of metal surface temperature. These observations suggest that the Pt and Pd crystallites in a supported catalyst are not significantly hotter than the alumina support in a microwave heated reactor.