Platinum catalysts supported on non-acidic materials have been prepared and characterized by electron microscopy (TEM), temperature programmed reduction (TPR), hydrogen chemisorption, and methylcyclopentane ring opening reaction. The analysis of the product distribution of this reaction has been shown to be a powerful tool in the study of morphological changes in the catalysts resulting from thermal treatments. Two catalyst series, Pt/L zeolites and Pt/Mg(Al)O, have been investigated using this test reaction. By combining TPR and TEM measurements with the analysis of the 3MP/2MP ratio in the products, it was shown that a high temperature calcination treatment on Pt/L zeolites resulted in a migration of the Pt species out of the zeolite channels. Similarly the analysis of TPR experiments and the MCP-RO selectivity to n-hexane over Pt/Mg(Al)O indicated that, during the preparation of the catalysts, a large fraction of Pt species became trapped inside the bulk of the support and came out to the surface only after a cycle of oxidation/reduction at relatively high temperatures.