The kinetics of the reaction between the radicals NO 3 and OClO have been investigated at low pressure and room temperature using three laboratory techniques: discharge stopped-flow, slow-flow, and discharge-flow. In all types of experiment, strong evidence was found to suggest that reaction between the two species occurred on the walls of the reaction cell and led to the release of ClO into the gas phase. No evidence was found for the occurrence of the homogeneous reaction NO 3 + OClO f products, and an upper limit for the rate coefficient for this process of 6 × 10 -17 cm 3 molecule -1 s -1 was determined. These experimental results are in disagreement with those of a previous study and suggest that this gas-phase reaction is unlikely to be of atmospheric importance even in the regions of the nighttime stratosphere where both species coexist.Kinetic Studies of the Reaction between NO 3 and OClO