The N-15 and O-18 kinetic isotope effects (KIEs) in the catalytic decomposition of nitrous oxide on NiO powder were determined in the temperature range of 625-825 K, and the following temperature dependencies were found: KIE(N-15) = (0.821 +/- 0.180) + (1445 +/- 128)/T and KIE(O-18) = (1.384 +/-0.124) + (1450 +/- 89)/T. At initial pressures of N2O between 40 and 60 kPa, the reaction is first order in N2O and has an apparent activation energy of 131 +/- 3 kJ mol(-1). According to Bigeleisen's formalism, a bent, product-like NNO transition state and a fork-type NNOO transition state best fit the experimental results.