The rate coefficient for reaction 1, Cl + ClONO2 --> products was measured between 195 and 354 K. Cl atoms were generated by pulsed laser photolysis of Cl-2 in an excess of ClONO2. The temporal profiles of Cl atom loss and NO3 product formation were monitored using resonance fluorescence and tunable diode laser absorption at 662 nm, respectively, The long path absorption system was used to measure k(1) between 200 and 298 K while the resonance fluorescence system was employed between 195 and 354 K. Thermal decomposition of ClONO2 prevented measurements at temperatures greater than 354 K. The two techniques yielded rate coefficients which are in excellent agreement, An Arrhenius rate coefficient expression of k(1) = (6.0 +/- 0.4) x 10(-12) exp[(140 +/- 30)/T] cm(3) molecule(-1) s(-1) and room temperature rate constant of k(1)(298 K) (9.6 +/- 1.0) x 10(-12) cm(3) molecule(-1) s(-1) were derived from data at T less than or equal to 298 K. The quoted error limits are 2 sigma and include estimated systematic errors. Our results are compared with previous measurements, and values of k(1) for atmospheric modeling are recommended.