Hydrogen for use in fuel cells is typically generated in a fuel processor from available fuels (CnHmOp) by means of the reforming reaction. In this article, we describe the reforming process, discuss the three principal pathways (steam reforming, partial oxidation, and autothermal reforming), and demonstrate that the process is most efficient when conducted under conditions of thermoneutrality (ΔHr=0). The reforming efficiency is correlated with the fuel properties to show that it depends on the values of n and m, and on the heat of formation of the fuel. Steam reforming is known to produce high concentrations of hydrogen in the product. The partial oxidation and autothermal reforming processes are more attractive for practical applications; contrary to widely held beliefs, they are also capable of higher reforming efficiencies than are steam reformers.