The non-catalytic autothermal gasification of woody biomass with air and steam mixtures is thermodynamically and experimentally investigated. A laboratory-scale fixed-bed downdraft reactor was used to gasify fine-grained woody biomass particles (German conifer, mean particle size = 133.7 mu m) at atmospheric pressure and at 900-1020 K, with an equivalence ratio (ER) in the range 0.3-0.4 and a steam-to-biomass ratio (SB) in the range 0-0.6. The gasification efficiency and carbon conversion peaked at 35% and 83%, respectively, for ER = 0.4 and SB = 0.6. Hydrogen yield increased with both ER and SB within the ranges considered. The corresponding volumetric lower heating value of the dry gaseous product varied from 2.0 to 3.4 MJ/Nm(3). Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.