The pyrolysis of southern pine, red oak, and sweet gum sawdust is reported. Pyrolysis experiments were conducted under either a helium or nitrogen atmosphere at similar to 371-871 degrees C, to determine the balance between liquid and gas products. Gas- and liquid-phase pyrolysis products were identified using gas chromatography (GC) and GC/mass spectrometry (MS). A total of 109 liquid and 40 gas compounds were identified. A total of 59 chemical compounds (35 liquids and 24 gaseous products) were quantitatively determined. The influence of the gas-phase residence time and biomass feed particle size were studied. The gas residence time determined the extent of secondary reactions. Very short residence times enhanced liquid production versus gas production. Particle sizes (d < 105 mu m, 105 mu m < d < 149 mu m, 149 mu m < d < 297 mu m, and d > 297 mu m) did not have a pronounced effect on either the yield or product distributions, indicating that heat-transfer limitations within the particles were negligible. The pyrolysis of pine, red oak, and sweet gum sawdust yielded similar product distributions. Simulations were conducted using the ASPEN/SP software package based on Gibbs energy minimization. At high temperatures, dominant species were hydrogen and carbon monoxide, while at lower temperatures, methane, carbon dioxide, and water were the predominant species. Above 871 degrees C, further increases in the temperature did not affect the product distribution. Lower gasification temperatures and higher steam/carbon ratios resulted in higher hydrogen and carbon monoxide production.