Three basic concepts of solid oxide fuel cell (SOFC) systems operating on hydrocarbon fuels, with external, internal, and partial prereforming, respectively, are presented and discussed. Internal reforming of methane is advantageously used for additional cooling of the SOFC stack, thus increasing system efficiency. Basic thermodynamics, catalysis, and kinetics of the methane steam reforming process are presented. Examples of SOFC stacks operating on internal reforming of methane and simulated partial prereforming of mine gas and natural gas are discussed. The latter is used to illustrate the effect of internal methane reforming on heat management in SOFC stacks.