The dissociation of ethane into two methyl radicals has been investigated at 566 and 600° and pressures over the range 0.4-300 mm. Reaction rates have been determined by measuring the rates of formation of methane by the subsequent reaction CH3+ C2H6→C2H5+ CH4. The first-order rate coefficients for the dissociation reaction decrease measurably with pressure at pressures below 100 mm. The variations have been compared with those predicted by the Kassel theory and by the Rice-Ramsperger-Kassel-Marcus theory of unimolecular reactions. Only the latter theory is in satisfactory agreement with the experimental data. On the assumption there is a favourable comparison between the results of this work and those obtained for the combination of methyl radicals at 247°, the Kassel theory may be used to predict the change in “fall-off” behaviour with temperature. The overall mechanism for the thermal decomposition of ethane has been reconsidered in the light of the experimental observations.