Mathematical development of preliminary performance/design equations for a reformate/air fueled high temperature PBO (poly (p-phenylene -2, 6- benzobisoxazole))/ PBI (poly (benzimidazole))-based solid polymer electrolyte fuel cell is presented. This development is based on the principles of transport phenomena, intrinsic electro-chemical kinetics, and thermodynamics. The formulated equations give a quantitative 2-d description of the mass fraction profiles of the chemical species, such as hydrogen, oxygen, nitrogen, carbon dioxide, and water, within the fuel cell. These equations for the mass fraction profiles in the anode/cathode diffusion and electrochemical reaction layers were developed as a function of the distance in the proton transport direction and the distance axially along the cell anode/cathode flow channels. Given cell geometry and chemical species transport and intrinsic electrochemical kinetic parameters, the developed equations can be employed to compute the local mass fluxes and predict the anode and cathode cell overvoltages.