The kinetics of the gas-phase reactions of chlorine atoms with fluoromethane (CH3F) and D-fluoromethane (CD3F) was studied experimentally. The relative rate method was applied using Cl + CH4 as the reference reaction. The rate constants for H-abstraction from CH3F (k(H)) and D-abstraction from CD3F (k(D)) were measured in the temperature range of 298-527 K and at a total pressure of 100 Torr using N-2 as a diluent. The temperature dependency of the rate constants are described by the expressions: k(H) = (1.65 +/- 0.26) x 10(-11) x exp(-1150 +/- 30/T) and k(D) = (1.21 +/- 0.14) x 10(-11) x exp(-1600 +/- 25/T) cm(3) molecule(-1) s(-1). The kinetic isotope effect, described by the ratio k(H)/k(D), was found to be 6.2 +/- 0.4 at room temperature. (C) 2012 Elsevier B.V. All rights reserved.