The thermal dissociation of N2O in argon was investigated by monitoring the formation of O(P-3) atoms in the reflected shock regime using atomic resonance absorption spectrophotometry (ARAS). The total density and [N2O] ranges were, (2.6 x 10(18))-(5.4 x 10(18)) molecules cm(-3) and (3.3 x 10(12))-(7.9 x 10(15)) molecules cm(-3), respectively. Values for the bimolecular rate constant (131 points), derived under low-pressure limit conditions are given by the Arrhenius expression : k(1)(T) = (1.18 +/- 0.16) x 10(-9) exp[(-57820 +/- 460 cal mol(-1))/RT] cm(3) molecule(-1) s(-1) for the temperature range, 1195 less than or equal to T less than or equal to 2384 K. These results extend the low-temperature range of ARAS measurements of k(1) by about 200 degrees C which is very significant in 1/T; and the value of the rate constant was extended by more than an order of magnitude. The present data were combined with previously published ARAS data to form a composite data set with a total of 278 points. Although systematic differences between the data of the various groups were discernible, all the data are well represented by the following Arrhenius equation : k(1)(T) = (9.52 +/- 1.07) x 10(-10) exp[(-57570 +/- 390 cal mol(-1))/RT] cm(3) molecule(-1) s(-1) for the temperature range, 1195 less than or equal to T less than or equal to 2494 K). Uncertainties in the Arrhenius expression are given at the one standard deviation level and the mean deviation of the experimental data from that predicted by the expression is +/-26%. These results are compared to those from previous experimental studies, The rate of the reaction of O(P-3) with N2O was investigated experimentally and by kinetic modeling, but only over a limited temperature range, 1200 less than or equal to T less than or equal to 1400 K. Upper limit values of the overall rate constant for the O(P-3) + N2O reaction were estimated by a statistical technique. These values were about a factor of 10 lower (with an overall uncertainty of about a factor of three) than those calculated from the recommended Arrhenius expressions of Baulch et al. (1973), Hanson and Salimian (1984), and Tsang and Herron (1991).