Two zone equilibrium and kinetic free model proposed by the authors in their earlier work [Ratnadhariya JK, Channiwala SA. Two zone equilibrium and kinetic free modeling of gasifier. Proceedings of the 12th European Conference and Technical Exhibition on Biomass for Energy, Industry and Climate Protection. Amsterdam, The Netherlands: 2002. p. 813-816], offers gas composition, temperature profile and gasifier performance parameters for two zones. This model does not predict composition and temperature profile of pyrolysis zone, which is stated to be a precursor for gasification. Looking to this fact a three zone equilibrium and kinetic free model of biomass gasifier is proposed in the present work. In this three zone: first zone of the model is drying and pyrolysis zone combined together: second zone is oxidation zone; and the third zone is the reduction zone. Each zone has been formulated with: (i) reaction stoichiometry; (ii) constituent balance: and (iii) energy balance along with a few justifying assumptions. This model clearly provides an operating range of equivalence ratio and moisture content for the woody biomass materials. Further, this model facilitates the prediction of the maximum temperature in the oxidation zone of gasifier, which provides useful information for the design of the gasifier and selection of the material for the construction. The merits of the model lies in the fact that it is capable of handling predictions for all category of biomass materials with a wide operating range of equivalence ratio and moisture content in all of the three principal zones of the gasifier. (C) 2008 Elsevier Ltd. All rights reserved.