The rate constants for the gas-phase reactions of ground-state oxygen atoms with CF2CFCl (1), (E/Z)-CFClCFCl (2), CFClCH2 (3), and (E/Z)-CFHCHCl (4) have been measured directly using a discharge flow tube coupled to a chemiluminescence detection system. The experiments were carried out under pseudo-first-order conditions with [O3P)]0 ≪ [ethene]0. The temperature dependences of the reactions were studied for the first time in the range 298–359 K. The proposed Arrhenius expressions (in units of cm3 molecule−1 s−1) were k1 = (1.07 ± 0.32) × 10−11 exp{−(8000±1600)/RT}, k2 = (0.56 ± 0.10) × 10−11 exp{−(8700±500)/RT}, k3 = (4.23 ± 1.25) × 10−11 exp{−(12,700 ± 800)/RT}, and k4 = (1.13 ± 0.62) × 10−11 exp{−(10,500 ± 1500)/RT}. All the rate coefficients display a positive temperature dependence, which highlights the importance of the irreversibility of the addition mechanism for these reactions. Halogen substitution in the ethene is discussed in terms of reactivity with O(3P). © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 763–769, 2005