The validity of the model developed for fluidized bed gasification of biomass was tested using experimental data obtained from a 400 kWthermal, dual-distributor-type fluidized bed gasifier. The fluidized bed was operated on wheat straw at various equivalence ratios, fluidization velocities, and bed heights. Both the predicted and the experimental bed temperatures increased linearly with the increase in equivalence ratio. At higher equivalence ratios (ER > 0·25) the model predictions for gas composition and the higher heating value were in good agreement with the experimental data. However, at lower equivalence ratios (ER < 0·20) the higher heating value of gas and the mole fractions of methane were overpredicted by the model This was because of the drastic increase in tar formation at such low equivalence ratios. The model predictions were improved substantially when the tar formation was included in the model.