Stratospheric N2O is known to be enriched in the heavy isotopes 15N and 18O relative to tropospheric N2O, primarily because of the preferential photolysis of light isotopologues. We present measurements of δ15N, δ18O, and site-specific δ15N on N2O from 32 stratospheric whole air samples collected by the NASA ER-2 aircraft between 1997 and 2000 from 62¿N to 89¿N with N2O mixing ratios ranging from 51 to 313 ppbv. The relationships between the isotopic compositions and N2O mixing ratios show significant differences between aircraft deployments and with previous measurements for N2O 200 ppbv and N2O 200 ppbv we conclude that the fluxes to the troposphere estimated from these relationships and, therefore, the influence of stratosphere-to-troposphere transport on the isotopic compositions of N2O in the free troposphere are now relatively well quantified, leaving the isotopic compositions of the N2O sources as the remaining largest uncertainties in the global N2O isotope budget.