Atmospheric samples were collected during rice straw burning at four different locations in Viet Nam during the dry and wet seasons (March 1992, February 1993, and August 1992, respectively). The samples were analyzed for CO2, CO, and COS. The emission ratios relative to CO2 for rice straw burning during the dry season were comparable to those observed on samples collected during burning of savanna in Africa or forest in the United States. On the contrary, during the wet season the emission ratios for CO and COS relative to CO2 were 2 to 10 times higher. With these emission ratios and estimates of rice production from southeastern Asia, we estimated that burning of rice straw emits annually about 2.1 Tmol of CO (25 Tg C) and 0.6 Gmol of COS (0.02 Tg S) to the atmosphere. Taking into account these new results, CO and COS fluxes from biomass burning could be reevaluated by 5–21% and 10–67%, respectively, with regard to previous estimates of these gas emissions from all biomass burning activities.