For a fluidized-bed gasifier, reaction conditions vary along the height of the reactor. Hence, the steam injection location may have a considerable effect on the syngas quality. The objective of this study was to investigate the effects of steam injection location and steam-to-biomass ratio (SBR) on the syngas quality generated from an air-steam gasification of switchgrass in a 2-5 kg/h autothermal fluidizedbed gasifier. Steam injection locations of 51, 152, and 254 mm above the distributor plate and SBRs of 0.1, 0.2, and 0.3 were selected. Results showed that the syngas H-2 and CO yields were significantly influenced by the steam injection location (p < 0.01) and SBR (p < 0.05). The steam injection location also significantly influenced hot and cold gas, as well as carbon conversion efficiencies. The best syngas yields (0.018 kg H-2/kg biomass and 0.513 kg CO/kg biomass) and gasifier efficiencies (cold gas efficiency of 67%, hot gas efficiency of 72%, and carbon conversion efficiency of 96%) were at the steam injection location of 254 mm and SBR of 0.2. (C) 2013 Elsevier Ltd. All rights reserved.