The rates of the hydrogen abstraction reactions of fluorine atoms with hydrogen, four alkanes and methyl chloride were measured in the gas phase using a competitive technique. The compounds were arranged in the following series in which adjacent pairs were competed for fluorine: (i) H2, CH4, C2H6, H2(ii)CH3Cl, C2H6, C3H8, CH3Cl. New values of the activation energy for CH4 and C2H6 of 1850±230 and 480±20 cal mol–1 respectively have been determined which are free from self-heating errors and are internally consistent when calculated from different competitive routes. A value of 2470±270 cal mol–1 for H2 has been similarly obtained, which differs from previously reported values based on erroneous values for methane and ethane.