The purification of biomass-derived syngas via tar abatement by catalytic steam reforming has been investigated using benzene, toluene, naphthalene, anthracene and pyrene as surrogated molecules. The effects of temperature and steam-to-carbon ratio on conversion, and the tendency towards coke formation were explored for each model compound. Two commercial nickel-based catalysts, the UCI G90-C and the ICI 46-1, were evaluated. The five tar model compounds had very different reaction rates. Naphthalene was the most difficult compound to steam reform, with conversions from 0.008 g(org-conv)/g(cat) min (790 degreesC) to 0.022 g(org-conv)/g(cat) min (890 degreesC) at an SIC ratio of 4.2. The most reactive compound was benzene, with a conversion of 1.1 g(org-conv)/g(cat) min at 780 degreesC and an SIC ratio of 4.3. The tendency towards coke formation grew as the molecular weight of the aromatic increased. The minimum SIC ratio for toluene was 2.5 at a catalyst temperature of 725 degreesC, and for pyrene at 790 degreesC it was 8.4. In general, catalyst temperatures and SIC ratios need to be higher than for naphtha in order to prevent the formation of coke on the catalyst.