The combination of gasification and solid oxide fuel cells (SOFCs) has the potential to improve efficiency and reduce emissions for fuels, such as coal and biomass. Gasification syngas is a mix of fuel gases containing contaminants, such as sulfur and tar, which have the potential to cause degradation of the materials used in the anode of the SOFC. In this study, nickelgadolinium-doped ceria (Ni-CGO) composites are exposed to syngas and toluene- and sulfur- (as CS2) contaminated syngas at temperatures from 600 to 765 degrees C to investigate the effects of the feed gases and contaminants on their reforming activity and the amount and type of carbon deposited. Under conditions favoring carbon deposition, a two-stage deactivation of the reforming activity is observed, with this being largely the same whether the syngas is pure or contaminated. Toluene-contaminated syngas does not increase the amount of carbon deposited or make it more difficult to remove graphitic carbon compared to uncontaminated syngas below 700 degrees C, but at 700 degrees C and above, it does increase the amount of carbon and produce more graphitic carbon. Syngas and toluene appear to compete for active sites, suggesting that the effects of tars and model tars on SOFCs need to be investigated under syngas rather than under hydrogen. Sulfur contamination reduces the amount of carbon deposition above 11 ppm of H2S.