The reaction of ethylene in engine exhaust gases has been studied using a turbulent plug flow reactor. The effects of ethylene, oxygen, and nitric oxide concentrations and of temperature on the reaction were investigated. Nitric oxide was found to be consumed in the reaction and partially converted to nitrogen dioxide. For temperatures up to 649 °C, little formation of carbon dioxide was measured for a reaction time of 140 ms. Increasing the oxygen concentration above 4% gave no increase in the oxidation rate. The Kinetics of the reaction were such that it was not possible to describe the reaction with a simple Arrhemus rate expression. The only other hydrocarbon found was a trace of acetylene at a reaction temperature of 649 °C.