We report studies of N2O concentrations in the ambient plumes of power plants. The results show that there is very little excess N2O within 100 m of the stack. There is some evidence that N2O is formed in the plumes father downwind. The magnitude of the effect cannot be quantitatively evaluated with the present data. Based on our results and published studies, we estimate that the global direct emissions of N2O from power plants are about 0.05 Tg/yr out of a total anthropogenic source of about 7 Tg/yr. ¿ American Geophysical Union 1992