XAFS, XRD, and TEM measurements on dispersed Pt/Al2O3 catalysts have elucidated the promotional effect of SO2 in propane oxidation over these systems. At low loadings (0.05 wt%), Pt/Al2O3 catalysts initially contain small (<20 Angstrom) stoichiometric beta-PtO2 particles. Catalyst sulphation is accompanied by reduction and concomitant sintering of these oxidic particles, resulting in metallic Pt clusters exhibiting similar structural and reactive properties to their counterparts formed at higher loading (9 wt%). The formation of stable SO4 species on both alumina support and on the Pt surface facilitates the dissociative chemisorption of propane onto both support and metal. Evidence is presented for the role of interfacial sulphate in the activation and subsequent oxidation of propane via a bifunctional mechanism,