The performance of a non-isothermal two-membrane reactor for reversible chemical reactions in gas phase has been analyzed by numerical simulation. The analyzed reactions were of the form : aA = bB + cC. Two membranes, that are permeable to all the components of the reaction mixture, are supposed to be the most permeable to one of the two reaction products, satisfying the condition of reverse products permselectivities. The reactant is taken to be the slowest permeating component. A negative temperature influence on the permeabilities of components has been assumed. Go-current plug flow pattern has been accepted. It has been shown that it is possible to enhance reactant conversion above that of a conventional reactor for both endothermic and exothermic reversible reactions, including adiabatic and non-adiabatic case. By using a two-membrane reactor, considerable lowering of feed temperatures is enabled for an endothermic reaction. For endothermic reactions, there is the optimum feed temperature, whereas for exothermic reactions, the higher the temperature, the lower is the attained conversion. In reactor design, the optimal external heat exchange for both endothermic and exothermic reactions can be determinated.