The rate of the reaction between H atoms and Cl2 was detd. in a discharge-flow system. By use of sensitive detection of H atoms by Lyman-a resonance fluorescence the reaction could be studied at low initial H atom concns. and unperturbed by interfering processes. From measurements in the temp. range T = 252-458 DegK, the Arrhenius expression k1 = (8.7 +- 1.7)1013exp(-5.0 +- 0.6 kJ mole-1/RT)cm3mole-1sec-1 can be derived.