N2O decomposition was examined over a series of Al2O3-Fe2O3 mixed oxidic solids with composition ranging from 0 to 100% Of Fe2O3. The catalytic activity of the solids runs parallel to the number of atoms of iron in the Al2-xFexO3 solid solution phase. Two compensation effects are present. The first corresponds to catalysts rich in alumina, and the second one to catalysts rich in hematite.