The experimental conditions under which a fluidized bed biomass gasifier can generate a gas with a tar content below 2 g/m(n)(3) are analyzed by using and developing the model recently published for those gasifiers by Corella and Sanz [Fuel Process. Techn. 2005, 86, 1021-1053]. The analyzed experimental conditions were: the equivalence ratio, the partitioning of the air, between the primary and secondary flows, the location (height) of the inlet of the secondary air flow, the biomass moisture and the biomass flow rate. Results from the modelling work are presented for a given CFB biomass gasifier of commercial size. Some of these results are also being checked in a CFB biomass gasifier at small pilot plant scale. To obtain a gasification gas with a very low tar content the two most important experimental conditions are a high value for the equivalence ratio and a good in-gasifier material which determines the values of the kinetic constants of the reactions involved in the network at the gasifier. (C) 2006 Elsevier B.V. All rights reserved.