The ClO radical plays a central role in the ClOx catalyzed destruction of O3 in the atm. and thus reactions that affect the availability of ClOx in the atm. are of interest to modelers of stratospheric chem. Rate consts. for the recombination reaction (1) ClO + NO2 (+ N2) -> ClONO2 (+ N2) were measured at 23-1040 mbar and 264, 298, and 343 K using flash photolysis to generate ClO radicals and time dependent UV absorption in the A-X system as their monitor. Values of k1 show a strong pressure dependence with an onset to fall-off at pressures .gtorsim.50 mbar. The fall-off behavior is interpreted in terms of complete and sym. Kassel integrals and is agreement with the accepted low pressure limit as well as with a theor. est. of the high pressure limiting rate const., k1... = 1.2 * 10-11 cm3/s.