The reduction of carbon in the vegetation and soils of Southeast Asia as a result of changes in land use since 1860 has been analyzed. Several independent estimates of deforestaion and of forest biomass were used to construct a range of esitimatis for the loss of carbon from the land. A net release of carbon to the atmosphere of between 8 and 19*10^15g was calculated for the period from 1860 to 1980. In 1980 the net release wasg C. The largest contributors to this release were the conversion of forests to shifting cultivation and the expansion of permanently cleared land. The greatest uncertainties in the anaylysis included estimates of the area cleared annually by shifting cultivators and the fate of those lands, and the lack of historical or current data on the extent of grasslands in Southeast Asia.