Four nitrous oxide (N2O) instruments werepart of the NASA ER-2 aircraft payload during the 2000 SAGE-III OzoneLoss and Validation Experiment (SOLVE). Coincident data from the threein situ instruments and a whole air sampler are compared. Agreementbetween these instruments was typically good; however, there areseveral types of important differences between the data sets. Thesedifferences prompted a collaborative effort to combine data from thethree in situ instruments, using an objective method, to produce aself-consistent, high-resolution, unified N2O data set foreach SOLVE flight. The construction method developed by the fourN2O instrument teams is described in detail. An importantstep in this method is the evaluation and reduction of bias in each ofthe in situ data sets before they are combined. The quality of unifiedN2O data is examined through its agreement withhigh-accuracy and high-precision N2O data from whole airsamples collected from the ER-2 during SOLVE flights. Typical agreementbetween these two data sets is 2.9 ppb (1.5%), better than the typicalagreement between any pair of N2O instruments.