Laboratory studies of the branching ratio of the reaction of electronically excited oxygen atoms, O(1D), with nitrous oxide, N2O, were performed by measuring the loss of N2O and the formation of products in a static optical cell interfaced to a Fourier transform spectrometer system. The results agree well with the most recent measurements, and a critical evaluation of the available data results in a factor of 2 reduction in the uncertainty. The ratio k1b/k1 is the fraction of reaction leading to the production of NO (reaction (1b)) relative to the total reaction of O(1D) with N2O (reaction (1)). The present recommendation for this ratio as it pertains to atmospheric reactions is 0.61¿0.08 (95% confidence interval). The consequences of this result in terms of stratospheric NOy production and field measurements of ozone photolysis rates are discussed.