We derive seasonal mean distributions of N2O as a function of latitude and height from in situ measurements made by the airborne tunable laser absorption spectrometer (ATLAS) instrument on board the NASA ER-2 aircraft. Seasonal means are also derived using an equivalent latitude coordinate which maximizes the information content and produces nearly pole-to-pole coverage. The mean N2O fields are consistent with the Brewer-Dobson circulation, showing tropospheric values of N2O entering the tropical lower stratosphere and low values at the winter hemisphere poles. The analysis presented here is intended for use as a climatology for two- and three-dimensional modelers wishing to evaluate the balance of transport processes affecting their models' lower stratosphere. We also present some interesting features that have been revealed by the high spatial resolution of the ATLAS measurements. These include large gradients of N2O observed at the equatorward and poleward edges of the surf zone and filaments less than 1 km thick identified during aircraft profiling. The results presented here demonstrate the unique nature and high value of aircraft in situ data sets. ¿ 1999 American Geophysical Union