Soils of tropical forests are the most important source of atmospheric N2O from natural ecosystems, but the extant flux estimates are based on a relatively small number of field measurements and simple extrapolation procedures. We present an empirical relationship between N2O and CO2 emissions from soils of Amazon tropical forest based on seven years of field measurements in Rond¿nia, Brazil. This relationship can be combined with estimates of soil CO2 emissions from existing biogeochemistry models to produce estimates of N2O emissions for tropical forest regions.