This work presents a detailed EXAFS study of platinum-modified sulfated zirconia catalysts that were prepared according to a three step method. which led to highly active and stable catalyst for n-pentane isomerization reaction. EXAFS carried out on the active catalysts prepared from sulfated zirconia calcined at higher temperature and reduction following impregnation with Pt, give evidence of large metallic Pt crystallites whereas similar catalysts prepared from sulfated zirconia calcined at lower temperature of 550 degreesC had mostly Pt-S co-ordination. The presence of the larger Pt crystallites seems necessary for arresting the rapid deactivation of the catalyst and increases its stability. (C) 2004 Elsevier B.V. All rights reserved.