The kinetics of the reaction HCl+ClONO2→Cl2+HNO3 were investigated at 298 K using a flow reactor of this reaction with FTIR analysis to assess the importance of this reaction for stratospheric chemistry. The observed reaction was characteristic of a heterogeneous process; an upper limit of 5¿10-18 cm3 molecule-1 s-1 was obtained for the homogeneous gas phase rate constant. From calculations of the first order wall rate constant, estimates were made of the reaction rate on stratospheric aerosols. Because both HCl and ClONO2 need to be adsorbed on the particle surface, the reaction will be of negligible importance under most stratospheric conditions.