Three kinds of Mn-containing perovskites, LaMnO3, La0.9MnO3 and LaMn0.9O3, have been investigated for methane combustion in the temperature range 475-600 degreesC. It has been possible to evidence that LaMn0.9O3 shows the greatest catalytic activity, probably because of its surface area, and also because its defect structure is favourable for development of active sites. The conversion observed as a function of temperature shows two ranges of well-defined slopes in the Arrhenius diagram and an explanation of this phenomenon is then formulated on the basis of the occurrence of diffusional limitations. The catalysts have been then characterised by means of temperature programmed desorption and reduction. TPD experiments have revealed two forms of surface oxygen species and in the higher temperature range investigated in activity experiments it is possible to argue a mobility between the two related types of sites: an interconversion between the two types of active species is therefore possible and can be decisive, as in the case of La0.9MnO3. (C) 2002 Elsevier Science B.V. All rights reserved.