Exhaust gas recirculation, EGR, can be used to produce hydrogen gas (H-2) via on board catalytic steam reforming, aiming at controlling emissions and mitigating loss of performance in downsized spark ignition engines. In the most straightforward design, the H-2-rich syngas produced by a reactor placed in the EGR line is mixed with the intake air. The EGR and reactor operate in a closed loop, starting in the exhaust and delivering syngas into the intake pipe. Here, a thermodynamic model is developed to evaluate the potential for onboard H-2 production in an direct injection ethanol fueled spark ignition engine with EGR. Chemical composition is predicted by assuming equilibrium at engine exhaust and at reactor outlet. Total engine mass flow rate, exhaust temperatures and pressures were adjusted to experimental data. The results indicated a potential to produce a molar concentration of 1% of H-2 in the intake mixture, for an engine speed of 5000 rpm. Decreasing engine speed causes a decrease in H-2 due to the lower engine exhaust temperature. Hot EGR presents a higher potential for heat recovery, but decreases substantially the heating value of the fuel by recirculation inert gases.