In steady state the stable isotopic composition of nitrogenand oxygen in tropospheric N-2O is balanced by isotopically light N-2O emitted from soils and oceans and isotopically heavy N-2O as a return flux from the stratosphere. However, no such balance was reached in calculations given by Kim and Craig (1993). Modifications have been made on their calculations based on the most recent reports on annual global emission of N-2O. It is considered that the nitrogen and oxygen isotope budget in tropospheric N-2O are approximately in balance if isotopic fractionation effects during the production of N-2O in soils and furthermore this paper puts forward further evidence for validating the above results. In steady state the stable isotopic composition of nitrogen and oxygen in tropospheric N - 2O is balanced by isotopically light N - 2O emitted from soils and oceans and isotopically heavy N - 2O as a return flux from the stratosphere. However, no such balance was reached in calculations given by Kim and Craig (1993). Modifications have been made on their most recent reports on annual global emission of N - 2O. It is considered that the nitrogen and oxygen isotope budget in tropospheric N - 2O are approximately in balance if isotopic fractionation effects during the production of N - 2O in soils and make this paper puts forward further evidence for validating the above results.