The kinetics of the reactions of chlorine nitrate with HCl and H2O have been investigated using a static photolysis/Fourier transform infrared spectrophotometer apparatus. Upper limits for the rate constants for the homogeneous gas-phase reactions of ClONO2+HCl (1) and ClONO2+H2O (2) were estimated to be <8.4¿10-21 and <3.4¿10-21 cm3 molec-1 s-1, respectively, at 296¿2 K. The yields of HNO3 were 1.05¿0.09 and 0.86¿0.08, respectively. No synergistic effect between H2O and HCl was observed. The kinetic behavior of reaction (2) was well described by simple first-order kinetics while the behavior of reaction (1) was found to be well described in terms of the Langmuir adsorptio isotherm.