The adsorption of carbonyl sulphide and hydrogen sulphide onto a range of supported platinum catalysts has been studied. The interaction between carbon monoxide and the sulphur-containing compounds was investigated by (i) preadsorbing carbon monoxide then adsorbing hydrogen sulphide or carbonyl sulphide, (ii) preadsorbing hydrogen sulphide or carbonyl sulphide followed by carbon monoxide adsorption, and (iii) coadsorption of carbon monoxide and the sulphur-containing compound. Isotopically labelled carbon monoxide was used to study the exchange processes occurring between carbonyl sulphide and carbon monoxide. In general, preadsorption of hydrogen sulphide blocked all carbon monoxide adsorption. On Pt/silica catalyst preadsorption of carbon monoxide reduced hydrogen sulphide adsorption by 81%. Coadsorption resulted in enhanced carbon monoxide adsorption on Pt/alumina and Pt/silica. On Pt/molybdena(I) (prepared by impregnation) the adsorption of both compounds was decreased, while on Pt/molybdena(C) (prepared firing a cocrystallized precursor), which was better dispersed, the adsorption capacity was unchanged. Adsorption of carbonyl sulphide was principally nondissociative. However, adsorption studies involving labelled carbon monoxide did reveal that a minority of the adsorbed carbonyl sulphide was dissociated on Pt/silica and on Pt/alumina (6 and 15%, respectively). No dissociation was detected on Pt/molybdena(I) and Pt/molybdena(C).