AbstractFlame propagation velocities and temperatures in composite stoichiometric mixtures H2/CH4/O2 at different compositions and dilution have been investigated.The experimental results show a weak interaction in the sense of a weak inhibition of hydrogen combustion by methane and a weak promotion of the methane combustion by hydrogen.The activation energy of the branching process in these composite mixtures lies between the values derived from experiments on the separate binary mixtures H2/O2 and CH4/O2.