Platinum is present in a metallic state following activation in air at 725 degrees C of both 5 wt% Pt/ZrO2 and 5 wt% Pt/SO42-/ZrO2. Reduction of either catalyst at 725 degrees C produces a Pt-Zr alloy, and these reduced catalysts, upon recalcination in air at 725 degrees C, form metallic Pt crystallites. Likewise, reduction of these uncalcined catalysts at 725 degrees C in H-2 leads to a Pt-Zr alloy formation. However, treatment of these uncalcined catalysts in H-2 at 450 degrees C does not produce Pt crystallites large enough to detect by XRD.