Biomass gasification in a fluidized bed with steam-O-2 mixtures has been studied in detail at pilot plant scale. The gasifier used was 15 cm i.d. and 3.2 m high, and it was fed with pine wood chips at flow rates of 5-20 kg/h. Main operating variables studied were gasifier bed temperature (780-890 degrees C), steam to oxygen in the feeding ratio (2-3 mol/mol), and gasifying agent (H2O + O-2) to biomass fed ratio (0.6-1.6 kg/kg daf). Product distribution here shown includes gas, tar and char yields, gas composition (H-2, CO, CO2, CH4, steam,...) and heating value, tar composition and content in the flue gas, gas heating value, apparent thermal efficiency, etc. Under good operating conditions the following gas is obtained : tar content of 5 g/Nm(3), 30 vol % H-2, heating value of 16.0 MJ/Nm(3) (dry basis), gas yield of 1.2 Nm(3) (dry basis)/kg biomass fed.