Biomass consumption and C02, CO and hydrocarbon gas emissions in an Amazonian forest clearing fire are presented and discussed. The experiment was conducted in the arc of deforestation, near the city of Alta Floresta, state of Mato Grosso, Brazil. The average carbon content of dry biomass was 48 percent and the estimated average moisture content of fresh biomass was 42 percent on wet weight basis. The fresh biomass and the amount of carbon on the ground before burning were estimated as 528 t/ha and 147 t/ha, respectively. The overall biomass consumption for the experiment was estimated as 23.9 percent. A series of experiments in the same region resulted in average efficiency of 40 percent for areas of the same size and 50 percent for larger areas. The lower efficiency obtained in the burn reported here occurred possibly due to rain before the experiment.