We report the development and application of analytical techniques for atmospheric N 2 O based on Fourier transform infrared (FTIR) spectroscopy. Using mobile low resolution (1 cm - 1 ) FTIR spectroscopy in the field, the technique delivers mixing ratio measurements of precision +/-0.3 ppbv (0.3 nmol mol - 1 ) N 2 O and in situ soil-atmosphere flux chamber measurements of fluxes less than 1 ngN m - 2 s - 1 (0.04 nmol N 2 O m - 2 s - 1 ) with a time resolution of 30 min. The method offers the additional advantages of being simultaneously able to measure CO 2 , CH 4 and CO mixing ratios in air to high precision (+/-0.15 μmol mol - 1 , +/-1 nmol mol - 1 , +/-0.3 nmol mol - 1 , respectively). By a similar analysis procedure, but with laboratory-based high resolution (0.012 cm - 1 ) FTIR spectroscopy, the N 2 O isotope ratios δ 1 5 N, δ 1 8 O and δ 1 7 O are determined simultaneously for a single sample, with current precision of +/-1.0%%,+/-2.5%% and +/-4.4%%, respectively. FTIR also resolves the individual contributions of the 1 5 N 1 4 N 1 6 O and 1 4 N 1 5 N 1 6 O to overall δ 1 5 N. The resolution of these two isotopomers is not possible using conventional isotope ratio mass spectrometry (IRMS). We present laboratory results demonstrating precision, and N-positionally resolved δ 1 5 N and δ 1 8 O measurements of UV-photolysed N 2 O in which a distinct asymmetric 1 5 N positional effect is observed.