A process for the production of ethylene from a methane rich gas stream and an ethane rich gas stream. The process comprises the steps of:(a) introducing the methane rich gas stream together with molecular oxygen into a lower zone of a fluidized-bed of particles which are catalytically active in promoting an exothermic oxidative coupling reaction to produce ethylene and other hydrocarbons,(b) mixing the ethane rich gas stream into the fluidized-bed above the level at which substantially all of the molecular oxygen has been consumed, and(c) subjecting the mixture resulting from step (b) to an endothermic pyrolysis reaction in an upper zone of the fluidized-bed to produce further ethylene and other olefinically unsaturated hydrocarbons.The process is characterized in that the pyrolysis step (c) is carried out substantially without the addition of heat to the reactor, other than the heat content of the methane rich and ethane rich gas streams and the heat generated by the exothermic oxidative coupling reaction. The fluidized bed particles are desirably caused to circulate within the reactor in such a manner that there is an efficient transfer of exothermic heat from the oxidative coupling zone to the pyrolysis zone so that the reactions of steps (a) and (c) occur at substantially the same temperature.