The impact of the main contaminants usually present in the gas generated during gasification of biomass was studied on a Pt-Rh/MgAl(O) reforming catalyst, which was exposed to solutions of K2SO4, KCl, and ZnCl2 and also to a leached solution of biomass fly ash by aerosol technology on a laboratory scale. The catalyst was exposed to a product gas of a bench-scale downdraft gasifier as well. Untreated and exposed catalysts were extensively characterized, and the extent of deactivation was examined in the steam reforming of methane under industrial-like conditions. The above treatments mainly affected the metal dispersion, but the catalyst achieved acceptable performances even after having been exposed to the biomass-generated gas. The noble metals system showed a lower activity than that of a highly loaded Ni commercial-like catalyst in gasifying conditions, but sintering and carbon formation were less pronounced.