The catalytic decomposition of N2O to N-2 and O-2 was carried out on the MxCo1-xCo2O4 (M = Ni2+ and Mg2+, x = 0.0-0.99) spinel catalysts. The results showed that the partial replacement of Co2+ by Ni2+ or Mg2+ in Co3O4 spinel oxide led to a significant improvement in the catalytic activity for the N2O decomposition, and the catalytic activity depended on the degree of Co2+ substitution by Ni2+ or Mg2+. The conversion of N2O reached 100% over the Ni0.74Co0.26Co2O4 and Mg0.54Co0.46Co2O4 catalysts at 200degreesC and 300degreesC in the absence and presence of excess O-2 and water steam, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.