The kinetics for the main reactions involved in the gasification of biomass are experimentally studied. The reactions concerned are: - devolatilisation (or pyrolysis) of the raw biomass; - oxidation of the raw biomass; - charcoal oxidation (attack by O2); - charcoal gasification (attack by CO2). Three commonly produced forms of biomass, i.e. rice husk, wheat straw and pine bark have been characterised. A bituminous coal has also been studied for reference to more classical fuels. Two reactors have been used. Dynamic Thermo-Gravimetry reproduces the low heating rates present in reactors such as fixed beds or rotary kilns. An entrained flow reactor was used to simulate the high heating rates encountered in fluidised beds, entrained beds and flash processes. Care was taken to remain in conditions where no heat transfer or mass transfer limitation is effective, so that intrinsic kinetic parameters could be determined. Quantitative values for the reaction rates in temperature domains relevant to industrial applications are derived. (Résumé d'auteur)