Gasification of some agricultural waste biomass samples (sunflower shell, pine cone, cotton refuse, and olive refuse) and colza seed was performed using a thermogravimetric analyzer at temperatures up to 1273 K with a constant heating rate of 20 K/min under a dynamic nitrogen-steam atmosphere. Derivative thermogravimetric analysis profiles of the samples were derived from the non-isothermal thermogravimetric analysis data. Gasification yields of the biomass samples at temperature intervals of 473-553 K, 553-653 K, 653-773 K, 773-973 K, and 973-1173 K were investigated considering the successive stages of "evolution of carbon oxides", "start of hydrocarbon evolution", "evolution of hydrocarbons", "dissociation", and "evolution of hydrogen", respectively. Although, there were some interactions between these stages, some evident relations were observed between the gasification yields in a given stage and the chemical properties of the parent biomass materials. (C) 2006 Elsevier B.V. All rights reserved.