The effect on performance of a solid oxide fuel cell-micro gas turbine (SOFC-MGT) hybrid system on mixing or replacing natural gas, the normal fuel of such hybrid systems, with biomass gasified fuel (biofuel) was studied. It was found that the efficiencies of the SOFC module and of the hybrid system noticeably decrease when natural gas is completely replaced by biofuel but that the system can still be, operated at a reasonable condition. To explain these results, changes in spatial distributions of temperature and concentration of certain chemical species inside an internal reforming type SOFC module are also discussed. (C) 2008 The Electrochemical Society.