The combustion of two agricultural residues, grape and olive bagasses, has been studied. The influence of oxygen partial pressure and gas flow rate have been analysed. The analysis of residual gases, mainly containing CO and CO2, shows that there are two successive stages or effects owing to the combustions of volatile compounds and solid. Oxygen partial pressure has a pronounced influence on the temperatures at which combustion effects are observed. In fact, both temperatures of combustion coincide when oxygen partial pressure is higher than 5 x 10(4) Pa. For each run, curves of weight loss and differential weight loss have been followed. From a kinetic model proposed (first and nth-reaction order, between 0 . 87 and 0 . 84, with respect to the solid and oxygen, respectively), the activation energy of combustion was found to be between 82 . 6 and 89 . 3 kJ mol(-1).