The catalytic reforming of methane by steam is an important industrial process that produces H-2, CO and CO2, thus chemically transforming natural gas, coal gas and light hydrocarbon feedstocks to synthesis gas or hydrogen fuel. Methane-steam reforming may consist of a number of reactions depending on the reforming catalyst, operating conditions and feedstock composition. The typical industrially desirable reactions are the reverse of methanation (CH4 + H2O = CO + 3H(2)) and the water-gas shift (CO + H2O = CO2 + H-2). Both reactions are equilibrium limited and the composition of the mixture that exits the reformer is in accordance with the one calculated thermodynamically. Removal of reaction products at the reactor exit by means of selective membrane permeation can offer improved CH4 conversions and CO2 and H-2 yields, assuming the subsequent utilization of the reject streams by a second methane-steam reformer. We numerically investigated the feasibility of a system of two tubular methane-steam reformers, in series with an intermediate permselective polyimide membrane permeator, as means of improving the overall CH4 conversion and the H-2, CO2 yields over conventional methane-steam reforming equilibrium reaction-separation schemes that are currently in industrial practice. The unique feature of the permselective polyimide separator is the simultaneous removal of H-2 and CO2 versus CH4 and CO from the reformed streams. The utilized 6FDA-3,3＇,5,5＇-TMB aromatic polyimide was reportedly characterized [10] and found to exhibit superior permselective properties compared with other polyimides of the same or different dianhydride sequence. Conversion and yield of the designed reactor-membrane permeator reforming system can be maximized by optimizing the permselective properties of the membrane material and the design variables of the reactors and the permeator. Product recovery and purity in the permeate stream need to be compromised to overall enhance methane conversion and product yield. The operating variables that were varied to investigate their effect on the magnitude of conversion and yield included the inlet pressure of the first reformer, the temperature of both reformers, and the permeator dimensionless Pe＇ number (variation of the first two variables results to a drastic change in the composition of the reformed stream that enters into the permeator). The numerical results show that the new reformer-membrane permeator cascade process can be more effective (it can offer increased CH4 conversions and H-2, CO2 yields) than conventional equilibrium methane-steam reforming reaction separation processes currently in practice.