The reaction of H atoms with N2O has been studied by flash photolysis in the temperature range 374–628 K at a pressure of 300 Torr, with argon as the bath gas. H atoms were generated by photolysis of NH3 and were monitored by Lyman-α absorption. At these temperatures the reaction is slow, and care was taken to establish conditions that ensured the measured rate constants were not affected by the occurrence of heterogeneous or secondary reactions. The values obtained are a factor of two less than those reported previously (Marshall etal., J. Chem. Phys., 1987, 86, 5540; J. Phys. Chem., 1989, 93, 1922) over this range of temperatures, and are given by Combination of our rate constants with earlier high temperature data (Albers etal., 15thInternationalSymposiumonCombustion, The Combustion Institute, Pittsburgh, PA, 1975, p. 765) confirms the curvature in the Arrhenius plot below 700 K observed previously. The combined data, for the temperature range 374–1110 K, can be represented by Simulation of the reaction shows that our results are consistent with the notion that the addition product HNNO is collisionally stabilized.