Structural transformation of bimetallic PdPt nanoparticles has been investigated with X-ray absorption near edge structure at high temperatures. PdPt bimetallic nanoparticles have been prepared on a La-doped alumina by a sequential loading of H2PtCl6 onto the Pd loaded catalyst. The results of extended X-ray absorption fine structure at Pd K and Pt L-III edges showed that Pt was surface-enriched or anchored on the Pd metal core with an increase of the Pt content. The structure of the obtained bimetallic PtPd nanoparticles seemed to be retained upon heating up to 1273 K under ambient condition. The measurement of catalytic activity of these PdPt bimetallic nanoparticles over methane combustion showed that the difference in activity with increasing and decreasing reaction temperatures was disappeared probably due to the synergistic effect of the formation of the PdPt bimetallic nanoparticles. (C) 2004 Elsevier B.V. All rights reserved.