Very little is known about the thermal field inside three-way catalytic converters. The purpose of this experimental work was to make a series of measurements on a dynamometer test stand, using a lambda-controlled EFI engine equipped with a three-way metallic catalytic converter instrumented with thermocouples, in order to record time-resolved and space-resolved temperature data under several different conditions.A programmed step-by-step inlet gas temperature increase (controlled by an electric heater) pointed out the effect of the catalytic reactions on monolith temperature. Interaction between the hot gas flow and the converter was examined by changes in inlet geometry as well as modifications in the thermal boundary conditions (insulation, fan cooling). The time and space resolved temperatures were recorded from cold start for the study of the catalyst activation.Finally, engine misfiring was imposed in order to reach very high temperature changes inside the converter. Increments of 300°C were measured with a misfiring rate of 33 % which lasted 10 seconds, and the movement of the temperature peak in the metallic monolith was clearly observed. Following the misfiring cycle, the initial thermal conditions were restored after 20 seconds of normal engine running.