Torrefaction is a thermal treatment used to improve the properties of biomass in relation to thermochemical processing techniques for energy generation. It is a thermo-chemical treatment method primarily characterized by an operating temperature within the 200-300 ?C range. It is carried out under conditions of atmospheric pressure and in the presence of a minimum amount of oxygen in order to avoid spontaneous combustion. The aim of this study was to evaluate the combined effect of the temperature (240 and 280 ?C) and oxygen concentration (2, 6, 10 and 21%) on the physical and chemical properties of large particles of Eucalyptus grandis. A statistical analysis was carried out. The different oxygen concentrations did not significantly affect the composition of the solid by-product for low temperatures. At 280 ?C, the high oxygen concentration affected some of the properties studied.